diff --git a/src/main/scala/com/codecommit/antixml/NodeSeqSAXHandler.scala b/src/main/scala/com/codecommit/antixml/NodeSeqSAXHandler.scala
index bdf083a..64c345b 100644
--- a/src/main/scala/com/codecommit/antixml/NodeSeqSAXHandler.scala
+++ b/src/main/scala/com/codecommit/antixml/NodeSeqSAXHandler.scala
@@ -59,7 +59,13 @@ class NodeSeqSAXHandler extends DefaultHandler2 {
   }
 
   override def startPrefixMapping(prefix: String, namespace: String) {
-    scopes ::= (scopes.headOption map { _ + (prefix -> namespace) } getOrElse Map())
+    // This is an optimization to not generate a new map if the mapping exists
+    // already.
+    val parentScope = scopes.headOption getOrElse Map()
+    scopes ::= (if (parentScope.get(prefix) == Some(namespace))
+    	parentScope
+      else 
+        parentScope + (prefix -> namespace) )
   }
 
   override def endPrefixMapping(prefix: String) {
diff --git a/src/main/scala/com/codecommit/antixml/StAXParser.scala b/src/main/scala/com/codecommit/antixml/StAXParser.scala
index 10a85d8..7d7697c 100644
--- a/src/main/scala/com/codecommit/antixml/StAXParser.scala
+++ b/src/main/scala/com/codecommit/antixml/StAXParser.scala
@@ -92,9 +92,13 @@ class StAXParser extends XMLParser {
           var prefixes = prefixMapping.headOption getOrElse Map()
           while (i < xmlReader.getNamespaceCount) {
             val ns = xmlReader.getNamespaceURI(i)
-            val prefix = xmlReader.getNamespacePrefix(i)
-            // TODO: Only change if mapping doesn't exists already
-            prefixes = prefixes + (prefix -> ns)
+            val rawPrefix = xmlReader.getNamespacePrefix(i)
+            val prefix = if (rawPrefix != null) rawPrefix else "" 
+
+            // To conserve memory, only save prefix if changed
+            if (prefixes.get(prefix) != Some(ns)) {
+              prefixes = prefixes + (prefix -> ns)
+            }
             i = i + 1
           }
           prefixMapping ::= prefixes
diff --git a/src/main/scala/com/codecommit/antixml/XMLSerializer.scala b/src/main/scala/com/codecommit/antixml/XMLSerializer.scala
new file mode 100644
index 0000000..c911c61
--- /dev/null
+++ b/src/main/scala/com/codecommit/antixml/XMLSerializer.scala
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2011, Daniel Spiewak
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ * - Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer. 
+ * - Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * - Neither the name of "Anti-XML" nor the names of its contributors may
+ *   be used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.codecommit
+package antixml
+
+import java.io.Writer
+import java.io.File
+import java.io.FileOutputStream
+import java.io.OutputStreamWriter
+ 
+class XMLSerializer(val encoding : String, val outputDeclaration : Boolean) {
+  def serializeDocument(elem : Elem, w : Writer) {
+    if (outputDeclaration) {
+      w.append("<?xml version=\"1.0\" encoding=\"")
+      w.append(encoding )
+      w.append("\" standalone=\"yes\"?>")
+    }
+    serialize(elem, w);
+  }
+
+  def serializeDocument(elem : Elem, outputFile : java.io.File) {
+    serializeDocument(elem, new OutputStreamWriter(new FileOutputStream(outputFile), encoding))
+  }
+  
+  def serialize(elem : Elem, w : Writer) {
+    var scopes : List[Map[String, String]] = Nil;
+
+    def doSerialize(node : Node, w : Writer) {
+
+      node match {
+        case Elem(prefix, name, attrs, scope, children) => {
+          val parentScope = scopes.headOption getOrElse Map()
+          scopes = scope :: scopes
+          val attrStr = if (attrs.isEmpty) 
+		      ""
+		    else
+		      " " + (attrs map { case (key, value) => key.toString + "=\"" + Node.escapeText(value) + '"' } mkString " ")
+		    
+		  val scopeChange = scope filter { case (key, value) => parentScope.get(key) != Some(value) }
+		  val prefixesStr = if (scopeChange.isEmpty) 
+		      ""
+		    else 
+		      " " + (scopeChange map {
+		        case (key, value) => (if (key == "") "xmlns" else "xmlns:" + key) + "=\"" + Node.escapeText(value) + '"' } mkString " ")
+		
+		  val qname = (prefix map { _ + ":" } getOrElse "") + name
+		  val partial = "<" + qname + attrStr + prefixesStr
+		  if (children.isEmpty) {
+		    w append partial
+		    w append "/>"
+		  } else {
+			w append partial
+			w append '>'
+		  	children.foreach(doSerialize(_, w))
+		  	w append "</"
+			w append qname
+			w append '>'
+		  }
+          scopes = scopes.tail
+        }
+        case node => w.append(node.toString())
+      }
+    }
+    doSerialize(elem, w)
+  }
+}
+
+object XMLSerializer {
+	def apply(encoding : String = "UTF-8", outputDeclaration : Boolean = false) : XMLSerializer = {
+	  new XMLSerializer(encoding, outputDeclaration);
+	}
+}
\ No newline at end of file
diff --git a/src/main/scala/com/codecommit/antixml/node.scala b/src/main/scala/com/codecommit/antixml/node.scala
index d5dcd8b..a311103 100644
--- a/src/main/scala/com/codecommit/antixml/node.scala
+++ b/src/main/scala/com/codecommit/antixml/node.scala
@@ -118,24 +118,10 @@ case class Elem(prefix: Option[String], name: String, attrs: Attributes, scope:
   def canonicalize = copy(children=children.canonicalize)
   
   override def toString = {
-    import Node._
-    
-    val attrStr = if (attrs.isEmpty) 
-      ""
-    else
-      " " + (attrs map { case (key, value) => key.toString + "=\"" + escapeText(value) + '"' } mkString " ")
-    
-    val prefixesStr = if (scope.isEmpty) 
-      ""
-    else
-      " " + (scope map { case (key, value) => (if (key == "") "xmlns" else "xmlns:" + escapeText(key)) + "=\"" + escapeText(value) + '"' } mkString " ")
-
-    val qname = (prefix map { _ + ":" } getOrElse "") + name
-    val partial = "<" + qname + attrStr + prefixesStr
-    if (children.isEmpty)
-      partial + "/>"
-    else
-      partial + '>' + children.toString + "</" + qname + '>'
+    val sw = new java.io.StringWriter() 
+    val xs = XMLSerializer()
+    xs.serialize(this, sw)
+    sw.toString
   }
   
   def toGroup = Group(this)
diff --git a/src/test/scala/com/codecommit/antixml/SAXSpecs.scala b/src/test/scala/com/codecommit/antixml/SAXSpecs.scala
index a6e1126..d51285f 100644
--- a/src/test/scala/com/codecommit/antixml/SAXSpecs.scala
+++ b/src/test/scala/com/codecommit/antixml/SAXSpecs.scala
@@ -42,6 +42,10 @@ class SAXSpecs extends Specification {
       SAXParser.fromString("<pf:a xmlns:pf='urn:a'/>") mustEqual Elem(Some("pf"), "a", Attributes(), Map("pf" -> "urn:a"), Group())
     }
 
+    "parse a simpleString with an non-prefixed namespace" in {
+      SAXParser.fromString("<a xmlns='urn:a'/>") mustEqual Elem(None, "a", Attributes(), Map("" -> "urn:a"), Group())
+    }
+
     "parse a String and generate an Elem" in {
       SAXParser.fromString("<p:a xmlns:p='ns'>hi<b attr='value' /> there</p:a>") mustEqual Elem(Some("p"), "a", Attributes(), Map("p"->"ns"), Group(Text("hi"), Elem(None, "b", Attributes("attr" -> "value"), Map("p"->"ns"), Group()), Text(" there")))
     }
diff --git a/src/test/scala/com/codecommit/antixml/StAXSpecs.scala b/src/test/scala/com/codecommit/antixml/StAXSpecs.scala
index af1b2b0..f6d4ce8 100644
--- a/src/test/scala/com/codecommit/antixml/StAXSpecs.scala
+++ b/src/test/scala/com/codecommit/antixml/StAXSpecs.scala
@@ -38,5 +38,10 @@ class StAXSpecs extends Specification {
       
       StAXParser.fromString("<a:a xmlns:a='a'>hi<b attr='value' /> there</a:a>") mustEqual Elem(Some("a"), "a", Attributes(), Map("a" -> "a"), Group(Text("hi"), Elem(None, "b", Attributes("attr" -> "value"), Map("a" -> "a"), Group()), Text(" there")))
     }
+    
+    "parse a simpleString with an non-prefixed namespace" in {
+      StAXParser.fromString("<a xmlns='urn:a'/>") mustEqual Elem(None, "a", Attributes(), Map("" -> "urn:a"), Group())
+    }
+
   }
 }
diff --git a/src/test/scala/com/codecommit/antixml/XMLSpecs.scala b/src/test/scala/com/codecommit/antixml/XMLSpecs.scala
index 6c23c66..449677a 100644
--- a/src/test/scala/com/codecommit/antixml/XMLSpecs.scala
+++ b/src/test/scala/com/codecommit/antixml/XMLSpecs.scala
@@ -68,15 +68,14 @@ class XMLSpecs extends Specification {
       fromString("<my:test xmlns:my='urn:my-urn:quux'></my:test>").name mustEqual "test"
     }
 
-    "serialize prefixes" in {
-      fromString("<my:test xmlns:my='urn:my-urn:quux'>\n<beef/>\n\t\n</my:test>").toString mustEqual "<my:test xmlns:my=\"urn:my-urn:quux\">\n<beef xmlns:my=\"urn:my-urn:quux\"/>\n\t\n</my:test>"
-    }
-
    "serialize prefixes minimally" in {
-     // fromString("<my:test xmlns:my='urn:my-urn:quux'>\n<beef/>\n\t\n</my:test>").toString mustEqual "<my:test xmlns:my=\"urn:my-urn:quux\">\n<beef/>\n\t\n</my:test>"
-     Pending("not implemented yet")
+     fromString("<my:test xmlns:my='urn:my-urn:quux'>\n<beef/>\n\t\n</my:test>").toString mustEqual "<my:test xmlns:my=\"urn:my-urn:quux\">\n<beef/>\n\t\n</my:test>"
    }
-  }
+
+   "serialize unprefixed elements correctly" in {
+     fromString("<test xmlns='urn:my-urn:quux'>\n<beef/>\n\t\n</test>").toString mustEqual "<test xmlns=\"urn:my-urn:quux\">\n<beef/>\n\t\n</test>"
+   }
+}
   
   "fromSource" should {
     import scala.io.Source