diff --git a/devtools/bench_noreply.pl b/devtools/bench_noreply.pl
new file mode 100644
index 00000000..365c6825
--- /dev/null
+++ b/devtools/bench_noreply.pl
@@ -0,0 +1,51 @@
+#! /usr/bin/perl
+#
+use warnings;
+use strict;
+
+use IO::Socket::INET;
+
+use FindBin;
+
+@ARGV == 1 or @ARGV == 2
+    or die "Usage: $FindBin::Script HOST:PORT [COUNT]\n";
+
+# Note that it's better to run the test over the wire, because for
+# localhost the task may become CPU bound.
+my $addr = $ARGV[0];
+my $count = $ARGV[1] || 10_000;
+
+my $sock = IO::Socket::INET->new(PeerAddr => $addr,
+                                 Timeout  => 3);
+die "$!\n" unless $sock;
+
+
+# By running 'noreply' test first we also ensure there are no reply
+# packets left in the network.
+foreach my $noreply (1, 0) {
+    use Time::HiRes qw(gettimeofday tv_interval);
+
+    print "'noreply' is ", $noreply ? "enabled" : "disabled", ":\n";
+    my $param = $noreply ? 'noreply' : '';
+    my $start = [gettimeofday];
+    foreach (1 .. $count) {
+        print $sock "add foo 0 0 1 $param\r\n1\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "set foo 0 0 1 $param\r\n1\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "replace foo 0 0 1 $param\r\n1\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "append foo 0 0 1 $param\r\n1\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "prepend foo 0 0 1 $param\r\n1\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "incr foo 1 $param\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "decr foo 1 $param\r\n";
+        scalar<$sock> unless $noreply;
+        print $sock "delete foo $param\r\n";
+        scalar<$sock> unless $noreply;
+    }
+    my $end = [gettimeofday];
+    printf("update commands: %.2f secs\n\n", tv_interval($start, $end));
+}
diff --git a/doc/protocol.txt b/doc/protocol.txt
index c72f50ea..3d1d2e86 100644
--- a/doc/protocol.txt
+++ b/doc/protocol.txt
@@ -126,9 +126,10 @@ Storage commands
 
 First, the client sends a command line which looks like this:
 
-<command name> <key> <flags> <exptime> <bytes> [<cas unqiue>]\r\n
+<command name> <key> <flags> <exptime> <bytes> [noreply]\r\n
+cas <key> <flags> <exptime> <bytes> <cas unqiue> [noreply]\r\n
 
-- <command name> is "set", "add", "replace", "append", "prepend", or "cas"
+- <command name> is "set", "add", "replace", "append" or "prepend"
 
   "set" means "store this data".  
 
@@ -174,6 +175,12 @@ First, the client sends a command line which looks like this:
   Clients should use the value returned from the "gets" command
   when issuing "cas" updates.
 
+- "noreply" optional parameter instructs the server to not send the
+  reply.  NOTE: if the request line is malformed, the server can't
+  parse "noreply" option reliably.  In this case it may send the error
+  to the client, and not reading it on the client side will break
+  things.  Client should construct only valid requests.
+
 After this line, the client sends the data block:
 
 <data block>\r\n
@@ -245,7 +252,7 @@ Deletion
 
 The command "delete" allows for explicit deletion of items:
 
-delete <key> <time>\r\n
+delete <key> [<time>] [noreply]\r\n
 
 - <key> is the key of the item the client wishes the server to delete
 
@@ -261,6 +268,10 @@ delete <key> <time>\r\n
   (which means that the item will be deleted immediately and further
   storage commands with this key will succeed).
 
+- "noreply" optional parameter instructs the server to not send the
+  reply.  See the note in Storage commands regarding malformed
+  requests.
+
 The response line to this command can be one of:
 
 - "DELETED\r\n" to indicate success
@@ -285,17 +296,21 @@ non-existent key exists with value 0; instead, they will fail.
 
 The client sends the command line:
 
-incr <key> <value>\r\n
+incr <key> <value> [noreply]\r\n
 
 or
 
-decr <key> <value>\r\n
+decr <key> <value> [noreply]\r\n
 
 - <key> is the key of the item the client wishes to change
 
 - <value> is the amount by which the client wants to increase/decrease
 the item. It is a decimal representation of a 64-bit unsigned integer.
 
+- "noreply" optional parameter instructs the server to not send the
+  reply.  See the note in Storage commands regarding malformed
+  requests.
+
 The response will be one of:
 
 - "NOT_FOUND\r\n" to indicate the item with this value was not found
@@ -399,16 +414,17 @@ Other commands
 --------------
 
 "flush_all" is a command with an optional numeric argument. It always
-succeeds, and the server sends "OK\r\n" in response. Its effect is to
-invalidate all existing items immediately (by default) or after the
-expiration specified.  After invalidation none of the items will be returned
-in response to a retrieval command (unless it's stored again under the
-same key *after* flush_all has invalidated the items). flush_all doesn't
-actually free all the memory taken up by existing items; that will
-happen gradually as new items are stored. The most precise definition
-of what flush_all does is the following: it causes all items whose
-update time is earlier than the time at which flush_all was set to be
-executed to be ignored for retrieval purposes.
+succeeds, and the server sends "OK\r\n" in response (unless "noreply"
+is given as the last parameter). Its effect is to invalidate all
+existing items immediately (by default) or after the expiration
+specified.  After invalidation none of the items will be returned in
+response to a retrieval command (unless it's stored again under the
+same key *after* flush_all has invalidated the items). flush_all
+doesn't actually free all the memory taken up by existing items; that
+will happen gradually as new items are stored. The most precise
+definition of what flush_all does is the following: it causes all
+items whose update time is earlier than the time at which flush_all
+was set to be executed to be ignored for retrieval purposes.
 
 The intent of flush_all with a delay, was that in a setting where you
 have a pool of memcached servers, and you need to flush all content,
@@ -431,9 +447,10 @@ In response, the server sends
 "VERSION <version>\r\n", where <version> is the version string for the
 server.
 
-"verbosity" is a command with a numeric argument. It always                                                  
-succeeds, and the server sends "OK\r\n" in response. Its effect is to                                        
-set the verbosity level of the logging output.                                                               
+"verbosity" is a command with a numeric argument. It always succeeds,
+and the server sends "OK\r\n" in response (unless "noreply" is given
+as the last parameter). Its effect is to set the verbosity level of
+the logging output.
 
 "quit" is a command with no arguments:
 
diff --git a/memcached.c b/memcached.c
index c467e8e6..c255127c 100644
--- a/memcached.c
+++ b/memcached.c
@@ -372,6 +372,8 @@ conn *conn_new(const int sfd, const int init_state, const int event_flags,
     c->bucket = -1;
     c->gen = 0;
 
+    c->noreply = false;
+
     event_set(&c->event, sfd, event_flags, event_handler, (void *)c);
     event_base_set(base, &c->event);
     c->ev_flags = event_flags;
@@ -733,6 +735,12 @@ static void out_string(conn *c, const char *str) {
 
     assert(c != NULL);
 
+    if (c->noreply) {
+        c->noreply = false;
+        conn_set_state(c, conn_read);
+        return;
+    }
+
     if (settings.verbose > 1)
         fprintf(stderr, ">%d %s\n", c->sfd, str);
 
@@ -898,7 +906,7 @@ typedef struct token_s {
 #define KEY_TOKEN 1
 #define KEY_MAX_LENGTH 250
 
-#define MAX_TOKENS 7
+#define MAX_TOKENS 8
 
 /*
  * Tokenize the command string by replacing whitespace with '\0' and update
@@ -968,6 +976,23 @@ static void write_and_free(conn *c, char *buf, int bytes) {
     }
 }
 
+static inline void set_noreply_maybe(conn *c, token_t *tokens, size_t ntokens)
+{
+    int noreply_index = ntokens - 2;
+
+    /*
+      NOTE: this function is not the first place where we are going to
+      send the reply.  We could send it instead from process_command()
+      if the request line has wrong number of tokens.  However parsing
+      malformed line for "noreply" option is not reliable anyway, so
+      it can't be helped.
+    */
+    if (tokens[noreply_index].value
+        && strcmp(tokens[noreply_index].value, "noreply") == 0) {
+        c->noreply = true;
+    }
+}
+
 inline static void process_stats_detail(conn *c, const char *command) {
     assert(c != NULL);
 
@@ -1347,6 +1372,8 @@ static void process_update_command(conn *c, token_t *tokens, const size_t ntoken
 
     assert(c != NULL);
 
+    set_noreply_maybe(c, tokens, ntokens);
+
     if (tokens[KEY_TOKEN].length > KEY_MAX_LENGTH) {
         out_string(c, "CLIENT_ERROR bad command line format");
         return;
@@ -1418,6 +1445,8 @@ static void process_arithmetic_command(conn *c, token_t *tokens, const size_t nt
 
     assert(c != NULL);
 
+    set_noreply_maybe(c, tokens, ntokens);
+
     if(tokens[KEY_TOKEN].length > KEY_MAX_LENGTH) {
         out_string(c, "CLIENT_ERROR bad command line format");
         return;
@@ -1514,6 +1543,8 @@ static void process_delete_command(conn *c, token_t *tokens, const size_t ntoken
 
     assert(c != NULL);
 
+    set_noreply_maybe(c, tokens, ntokens);
+
     if (settings.managed) {
         int bucket = c->bucket;
         if (bucket == -1) {
@@ -1535,7 +1566,7 @@ static void process_delete_command(conn *c, token_t *tokens, const size_t ntoken
         return;
     }
 
-    if(ntokens == 4) {
+    if(ntokens == (c->noreply ? 5 : 4)) {
         exptime = strtol(tokens[2].value, NULL, 10);
 
         if(errno == ERANGE) {
@@ -1598,6 +1629,8 @@ static void process_verbosity_command(conn *c, token_t *tokens, const size_t nto
 
     assert(c != NULL);
 
+    set_noreply_maybe(c, tokens, ntokens);
+
     level = strtoul(tokens[1].value, NULL, 10);
     settings.verbose = level > MAX_VERBOSITY_LEVEL ? MAX_VERBOSITY_LEVEL : level;
     out_string(c, "OK");
@@ -1635,7 +1668,7 @@ static void process_command(conn *c, char *command) {
 
         process_get_command(c, tokens, ntokens, false);
 
-    } else if (ntokens == 6 &&
+    } else if ((ntokens == 6 || ntokens == 7) &&
                ((strcmp(tokens[COMMAND_TOKEN].value, "add") == 0 && (comm = NREAD_ADD)) ||
                 (strcmp(tokens[COMMAND_TOKEN].value, "set") == 0 && (comm = NREAD_SET)) ||
                 (strcmp(tokens[COMMAND_TOKEN].value, "replace") == 0 && (comm = NREAD_REPLACE)) ||
@@ -1644,11 +1677,11 @@ static void process_command(conn *c, char *command) {
 
         process_update_command(c, tokens, ntokens, comm, false);
 
-    } else if (ntokens == 7 && (strcmp(tokens[COMMAND_TOKEN].value, "cas") == 0 && (comm = NREAD_CAS))) {
+    } else if ((ntokens == 7 || ntokens == 8) && (strcmp(tokens[COMMAND_TOKEN].value, "cas") == 0 && (comm = NREAD_CAS))) {
 
         process_update_command(c, tokens, ntokens, comm, true);
 
-    } else if (ntokens == 4 && (strcmp(tokens[COMMAND_TOKEN].value, "incr") == 0)) {
+    } else if ((ntokens == 4 || ntokens == 5) && (strcmp(tokens[COMMAND_TOKEN].value, "incr") == 0)) {
 
         process_arithmetic_command(c, tokens, ntokens, 1);
 
@@ -1656,11 +1689,11 @@ static void process_command(conn *c, char *command) {
 
         process_get_command(c, tokens, ntokens, true);
 
-    } else if (ntokens == 4 && (strcmp(tokens[COMMAND_TOKEN].value, "decr") == 0)) {
+    } else if ((ntokens == 4 || ntokens == 5) && (strcmp(tokens[COMMAND_TOKEN].value, "decr") == 0)) {
 
         process_arithmetic_command(c, tokens, ntokens, 0);
 
-    } else if (ntokens >= 3 && ntokens <= 4 && (strcmp(tokens[COMMAND_TOKEN].value, "delete") == 0)) {
+    } else if (ntokens >= 3 && ntokens <= 5 && (strcmp(tokens[COMMAND_TOKEN].value, "delete") == 0)) {
 
         process_delete_command(c, tokens, ntokens);
 
@@ -1729,11 +1762,13 @@ static void process_command(conn *c, char *command) {
 
         process_stat(c, tokens, ntokens);
 
-    } else if (ntokens >= 2 && ntokens <= 3 && (strcmp(tokens[COMMAND_TOKEN].value, "flush_all") == 0)) {
+    } else if (ntokens >= 2 && ntokens <= 4 && (strcmp(tokens[COMMAND_TOKEN].value, "flush_all") == 0)) {
         time_t exptime = 0;
         set_current_time();
 
-        if(ntokens == 2) {
+        set_noreply_maybe(c, tokens, ntokens);
+
+        if(ntokens == (c->noreply ? 3 : 2)) {
             settings.oldest_live = current_time - 1;
             item_flush_expired();
             out_string(c, "OK");
@@ -1798,7 +1833,7 @@ static void process_command(conn *c, char *command) {
 #else
         out_string(c, "CLIENT_ERROR Slab reassignment not supported");
 #endif
-    } else if (ntokens == 3 && (strcmp(tokens[COMMAND_TOKEN].value, "verbosity") == 0)) {
+    } else if ((ntokens == 3 || ntokens == 4) && (strcmp(tokens[COMMAND_TOKEN].value, "verbosity") == 0)) {
         process_verbosity_command(c, tokens, ntokens);
     } else {
         out_string(c, "ERROR");
diff --git a/memcached.h b/memcached.h
index 826bb28a..3a9c6158 100644
--- a/memcached.h
+++ b/memcached.h
@@ -220,6 +220,7 @@ struct conn {
     int    bucket;    /* bucket number for the next command, if running as
                          a managed instance. -1 (_not_ 0) means invalid. */
     int    gen;       /* generation requested for the bucket */
+    bool   noreply;   /* True if the reply should not be sent. */
     conn   *next;     /* Used for generating a list of conn structures */
 };
 
diff --git a/t/noreply.t b/t/noreply.t
new file mode 100644
index 00000000..c1457b0b
--- /dev/null
+++ b/t/noreply.t
@@ -0,0 +1,53 @@
+#!/usr/bin/perl
+
+use strict;
+use Test::More tests => 10;
+use FindBin qw($Bin);
+use lib "$Bin/lib";
+use MemcachedTest;
+
+
+my $server = new_memcached();
+my $sock = $server->sock;
+
+
+# Test that commands can take 'noreply' parameter.
+print $sock "flush_all noreply\r\n";
+print $sock "flush_all 0 noreply\r\n";
+
+print $sock "verbosity 0 noreply\r\n";
+
+print $sock "add noreply:foo 0 0 1 noreply\r\n1\r\n";
+mem_get_is($sock, "noreply:foo", "1");
+
+print $sock "set noreply:foo 0 0 1 noreply\r\n2\r\n";
+mem_get_is($sock, "noreply:foo", "2");
+
+print $sock "replace noreply:foo 0 0 1 noreply\r\n3\r\n";
+mem_get_is($sock, "noreply:foo", "3");
+
+print $sock "append noreply:foo 0 0 1 noreply\r\n4\r\n";
+mem_get_is($sock, "noreply:foo", "34");
+
+print $sock "prepend noreply:foo 0 0 1 noreply\r\n5\r\n";
+my @result = mem_gets($sock, "noreply:foo");
+ok($result[1] eq "534");
+
+print $sock "cas noreply:foo 0 0 1 $result[0] noreply\r\n6\r\n";
+mem_get_is($sock, "noreply:foo", "6");
+
+print $sock "incr noreply:foo 3 noreply\r\n";
+mem_get_is($sock, "noreply:foo", "9");
+
+print $sock "decr noreply:foo 2 noreply\r\n";
+mem_get_is($sock, "noreply:foo", "7");
+
+print $sock "delete noreply:foo noreply\r\n";
+mem_get_is($sock, "noreply:foo");
+
+# Test that delete accepts both <time> and 'noreply'.
+print $sock "add noreply:foo 0 0 1 noreply\r\n1\r\n";
+print $sock "delete noreply:foo 10 noreply\r\n";
+print $sock "add noreply:foo 0 0 1 noreply\r\n1\r\n";
+# undef result means we couldn't add an entry because the key is locked.
+mem_get_is($sock, "noreply:foo");