diff --git a/Gemfile b/Gemfile
index 0a04e4e..b76e937 100644
--- a/Gemfile
+++ b/Gemfile
@@ -14,5 +14,4 @@ end
 
 group :test do
   gem 'cztop'
-  gem 'rbczmq'
 end
diff --git a/ci/Dockerfile.main.erb b/ci/Dockerfile.main.erb
index a1bc766..97dae5d 100644
--- a/ci/Dockerfile.main.erb
+++ b/ci/Dockerfile.main.erb
@@ -1,8 +1,6 @@
 FROM iruby-test-base:ruby-<%= ruby_version %>
 
-RUN gem install cztop \
-    && gem install rbczmq -- --with-system-libs
-
+RUN gem install cztop
 RUN mkdir -p /iruby
 ADD . /iruby
 WORKDIR /iruby
diff --git a/lib/iruby.rb b/lib/iruby.rb
index b4081be..bd68b1a 100644
--- a/lib/iruby.rb
+++ b/lib/iruby.rb
@@ -24,11 +24,7 @@
     begin
       require 'iruby/session/cztop'
     rescue LoadError
-      begin
-        require 'iruby/session/rbczmq'
-      rescue LoadError
-        STDERR.puts "Please install ffi-rzmq or cztop before running iruby. See README."
-      end
+      STDERR.puts "Please install ffi-rzmq or cztop before running iruby. See README."
     end
   end
 else
diff --git a/lib/iruby/session/rbczmq.rb b/lib/iruby/session/rbczmq.rb
deleted file mode 100644
index 625f27e..0000000
--- a/lib/iruby/session/rbczmq.rb
+++ /dev/null
@@ -1,72 +0,0 @@
-require 'rbczmq'
-
-module IRuby
-  class Session
-    include SessionSerialize
-
-    def initialize(config)
-      c = ZMQ::Context.new
-
-      connection = "#{config['transport']}://#{config['ip']}:%d"
-      reply_socket = c.socket(:ROUTER)
-      reply_socket.bind(connection % config['shell_port'])
-
-      pub_socket = c.socket(:PUB)
-      pub_socket.bind(connection % config['iopub_port'])
-
-      stdin_socket = c.socket(:ROUTER)
-      stdin_socket.bind(connection % config['stdin_port'])
-
-      Thread.new do
-        begin
-          hb_socket = c.socket(:REP)
-          hb_socket.bind(connection % config['hb_port'])
-          ZMQ.proxy(hb_socket, hb_socket)
-        rescue Exception => e
-          IRuby.logger.fatal "Kernel heartbeat died: #{e.message}\n#{e.backtrace.join("\n")}"
-        end
-      end
-
-      @sockets = { 
-        publish: pub_socket, reply: reply_socket, stdin: stdin_socket
-      }
-
-      @session = SecureRandom.uuid
-      unless config['key'].to_s.empty? || config['signature_scheme'].to_s.empty?
-        raise 'Unknown signature scheme' unless config['signature_scheme'] =~ /\Ahmac-(.*)\Z/
-        @hmac = OpenSSL::HMAC.new(config['key'], OpenSSL::Digest.new($1))
-      end
-    end
-
-    def description
-      'old-stle session using rbczmq'
-    end
-
-    # Build and send a message
-    def send(socket, type, content)
-      idents =
-        if socket == :reply && @last_recvd_msg
-          @last_recvd_msg[:idents]
-        else
-          type == :stream ? "stream.#{content[:name]}" : type
-        end
-      header = {
-        msg_type: type,
-        msg_id:   SecureRandom.uuid,
-        username: 'kernel',
-        session:  @session,
-        version:  '5.0'
-      }
-      @sockets[socket].send_message(ZMQ.Message(*serialize(idents, header, content)))
-    end
-
-    # Receive a message and decode it
-    def recv(socket)
-      @last_recvd_msg = unserialize(@sockets[socket].recv_message)
-    end
-
-    def recv_input 
-      unserialize(@sockets[:stdin].recv_message)[:content]["value"]
-    end
-  end
-end
diff --git a/lib/iruby/session_adapter.rb b/lib/iruby/session_adapter.rb
index 96f6f43..02f9448 100644
--- a/lib/iruby/session_adapter.rb
+++ b/lib/iruby/session_adapter.rb
@@ -36,14 +36,12 @@ def make_rep_socket(protocol, host, port)
 
     require_relative 'session_adapter/ffirzmq_adapter'
     require_relative 'session_adapter/cztop_adapter'
-    require_relative 'session_adapter/rbczmq_adapter'
     require_relative 'session_adapter/pyzmq_adapter'
 
     def self.select_adapter_class(name=nil)
       classes = {
         'ffi-rzmq' => SessionAdapter::FfirzmqAdapter,
         'cztop' => SessionAdapter::CztopAdapter,
-        'rbczmq' => SessionAdapter::RbczmqAdapter,
         # 'pyzmq' => SessionAdapter::PyzmqAdapter
       }
       if (name ||= ENV.fetch('IRUBY_SESSION_ADAPTER', nil))
diff --git a/lib/iruby/session_adapter/rbczmq_adapter.rb b/lib/iruby/session_adapter/rbczmq_adapter.rb
deleted file mode 100644
index 7158296..0000000
--- a/lib/iruby/session_adapter/rbczmq_adapter.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-module IRuby
-  module SessionAdapter
-    class RbczmqAdapter < BaseAdapter
-      def self.load_requirements
-        require 'rbczmq'
-      end
-
-      def send(sock, data)
-        sock.send_message(ZMQ::Message(*data))
-      end
-
-      def recv(sock)
-        sock.recv_message
-      end
-
-      def heartbeat_loop(sock)
-        ZMQ.proxy(sock, sock)
-      end
-
-      private
-
-      def make_socket(type, protocol, host, port)
-        zmq_context.socket(type).tap do |sock|
-          sock.bind("#{protocol}://#{host}:#{port}")
-        end
-      end
-
-      def zmq_context
-        @zmq_context ||= ZMQ::Context.new
-      end
-    end
-  end
-end
diff --git a/run-test.sh b/run-test.sh
index 2a5137e..eee3943 100644
--- a/run-test.sh
+++ b/run-test.sh
@@ -4,7 +4,7 @@ set -ex
 
 export PYTHON=python3
 
-ADAPTERS="cztop rbczmq ffi-rzmq pyzmq"
+ADAPTERS="cztop ffi-rzmq pyzmq"
 
 for adapter in $ADAPTERS; do
   export IRUBY_TEST_SESSION_ADAPTER_NAME=$adapter
diff --git a/test/iruby/session_adapter/rbczmq_adapter_test.rb b/test/iruby/session_adapter/rbczmq_adapter_test.rb
deleted file mode 100644
index c28e4ce..0000000
--- a/test/iruby/session_adapter/rbczmq_adapter_test.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-require_relative 'session_adapter_test_base'
-require 'iruby'
-
-module IRubyTest
-  if ENV['IRUBY_TEST_SESSION_ADAPTER_NAME'] == 'rbczmq'
-    class RbczmqAdapterTest < SessionAdapterTestBase
-      def adapter_class
-        IRuby::SessionAdapter::RbczmqAdapter
-      end
-
-      def test_send
-        dummy_message = MiniTest::Mock.new.expect(:called!, true)
-
-        dummy_socket = MiniTest::Mock.new.expect(:send_message, nil, [dummy_message])
-
-        ZMQ.stub(:Message, ->(message) { message.called!; message }) do
-          @session_adapter.send(dummy_socket, dummy_message)
-        end
-
-        assert(dummy_message.verify)
-        assert(dummy_socket.verify)
-      end
-
-      def test_recv
-        dummy_message = MiniTest::Mock.new
-        dummy_message.expect(:equal?, true, [dummy_message])
-
-        dummy_socket = MiniTest::Mock.new.expect(:recv_message, dummy_message)
-
-        assert_same(dummy_message, @session_adapter.recv(dummy_socket))
-
-        assert(dummy_message.verify)
-        assert(dummy_socket.verify)
-      end
-    end
-  end
-end
diff --git a/test/iruby/session_adapter_test.rb b/test/iruby/session_adapter_test.rb
index 81482da..862871e 100644
--- a/test/iruby/session_adapter_test.rb
+++ b/test/iruby/session_adapter_test.rb
@@ -12,27 +12,12 @@ def load_requirements
       refute subclass.available?
     end
 
-    def test_select_adapter_class_with_rbczmq
-      IRuby::SessionAdapter::RbczmqAdapter.stub :available?, true do
-        IRuby::SessionAdapter::CztopAdapter.stub :available?, false do
-          IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
-            IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
-              cls = IRuby::SessionAdapter.select_adapter_class
-              assert_equal IRuby::SessionAdapter::RbczmqAdapter, cls
-            end
-          end
-        end
-      end
-    end
-
     def test_select_adapter_class_with_cztop
       IRuby::SessionAdapter::CztopAdapter.stub :available?, true do
-        IRuby::SessionAdapter::RbczmqAdapter.stub :available?, false do
-          IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
-            IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
-              cls = IRuby::SessionAdapter.select_adapter_class
-              assert_equal IRuby::SessionAdapter::CztopAdapter, cls
-            end
+        IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
+          IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
+            cls = IRuby::SessionAdapter.select_adapter_class
+            assert_equal IRuby::SessionAdapter::CztopAdapter, cls
           end
         end
       end
@@ -40,12 +25,10 @@ def test_select_adapter_class_with_cztop
 
     def test_select_adapter_class_with_ffirzmq
       IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, true do
-        IRuby::SessionAdapter::RbczmqAdapter.stub :available?, false do
-          IRuby::SessionAdapter::CztopAdapter.stub :available?, false do
-            IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
-              cls = IRuby::SessionAdapter.select_adapter_class
-              assert_equal IRuby::SessionAdapter::FfirzmqAdapter, cls
-            end
+        IRuby::SessionAdapter::CztopAdapter.stub :available?, false do
+          IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
+            cls = IRuby::SessionAdapter.select_adapter_class
+            assert_equal IRuby::SessionAdapter::FfirzmqAdapter, cls
           end
         end
       end
@@ -54,30 +37,16 @@ def test_select_adapter_class_with_ffirzmq
     def test_select_adapter_class_with_pyzmq
       skip "pyzmq adapter is disabled"
       IRuby::SessionAdapter::PyzmqAdapter.stub :available?, true do
-        IRuby::SessionAdapter::RbczmqAdapter.stub :available?, false do
-          IRuby::SessionAdapter::CztopAdapter.stub :available?, false do
-            IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
-              cls = IRuby::SessionAdapter.select_adapter_class
-              assert_equal IRuby::SessionAdapter::PyzmqAdapter, cls
-            end
+        IRuby::SessionAdapter::CztopAdapter.stub :available?, false do
+          IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
+            cls = IRuby::SessionAdapter.select_adapter_class
+            assert_equal IRuby::SessionAdapter::PyzmqAdapter, cls
           end
         end
       end
     end
 
     def test_select_adapter_class_with_env
-      with_env('IRUBY_SESSION_ADAPTER' => 'rbczmq') do
-        IRuby::SessionAdapter::RbczmqAdapter.stub :available?, true do
-          assert_equal IRuby::SessionAdapter::RbczmqAdapter, IRuby::SessionAdapter.select_adapter_class
-        end
-
-        IRuby::SessionAdapter::RbczmqAdapter.stub :available?, false do
-          assert_raises IRuby::SessionAdapterNotFound do
-            IRuby::SessionAdapter.select_adapter_class
-          end
-        end
-      end
-
       with_env('IRUBY_SESSION_ADAPTER' => 'cztop') do
         IRuby::SessionAdapter::CztopAdapter.stub :available?, true do
           assert_equal IRuby::SessionAdapter::CztopAdapter, IRuby::SessionAdapter.select_adapter_class
diff --git a/test/iruby/session_test.rb b/test/iruby/session_test.rb
index 7a67e57..84a0924 100644
--- a/test/iruby/session_test.rb
+++ b/test/iruby/session_test.rb
@@ -22,8 +22,6 @@ def test_new_with_session_adapter
       adapter_class = case adapter_name
                       when 'cztop'
                         IRuby::SessionAdapter::CztopAdapter
-                      when 'rbczmq'
-                        IRuby::SessionAdapter::RbczmqAdapter
                       when 'ffi-rzmq'
                         IRuby::SessionAdapter::FfirzmqAdapter
                       when 'pyzmq'
@@ -39,12 +37,10 @@ def test_new_with_session_adapter
 
     def test_without_any_session_adapter
       IRuby::SessionAdapter::CztopAdapter.stub :available?, false do
-        IRuby::SessionAdapter::RbczmqAdapter.stub :available?, false do
-          IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
-            IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
-              assert_raises IRuby::SessionAdapterNotFound do
-                IRuby::Session.new(@session_config)
-              end
+        IRuby::SessionAdapter::FfirzmqAdapter.stub :available?, false do
+          IRuby::SessionAdapter::PyzmqAdapter.stub :available?, false do
+            assert_raises IRuby::SessionAdapterNotFound do
+              IRuby::Session.new(@session_config)
             end
           end
         end