diff --git a/app/models/content_instance.rb b/app/models/content_instance.rb
index 527c76ba..bef5cbd5 100644
--- a/app/models/content_instance.rb
+++ b/app/models/content_instance.rb
@@ -14,8 +14,7 @@ class ContentInstance
 
   ## validations ##
   validate :require_highlighted_field
-  validate :validate_uniqueness_of_slug
-  validates_presence_of :_slug
+  validates :_slug, :presence => true, :uniqueness => { :scope => :content_type_id }
 
   ## associations ##
   embedded_in :content_type, :inverse_of => :contents
@@ -77,9 +76,29 @@ class ContentInstance
 
   protected
 
+  # Sets the slug of the instance by using the value of the highlighted field
+  # (if available). If a sibling content instance has the same permalink then a
+  # unique one will be generated
   def set_slug
-    self._slug = self.highlighted_field_value.dup if self._slug.blank? && self.highlighted_field_value.present?
-    self._slug.permalink! if self._slug.present?
+    self._slug = highlighted_field_value.dup if _slug.blank? && highlighted_field_value.present?
+
+    if _slug.present?
+      self._slug.permalink!
+      self._slug = next_unique_slug if slug_already_taken?
+    end
+  end
+
+  # Return the next available unique slug as a string
+  def next_unique_slug
+    slug        = _slug.gsub(/-\d*$/, '')
+    last_slug   = _parent.contents.where(:_id.ne => _id, :_slug => /^#{slug}-?\d*?$/i).order_by(:_slug).last._slug
+    next_number = last_slug.scan(/-(\d)$/).flatten.first.to_i + 1
+
+    [slug, next_number].join('-')
+  end
+
+  def slug_already_taken?
+    _parent.contents.where(:_id.ne => _id, :_slug => _slug).any?
   end
 
   def set_visibility
@@ -98,12 +117,6 @@ class ContentInstance
     end
   end
 
-  def validate_uniqueness_of_slug
-    if self._parent.contents.any? { |c| c._id != self._id && c._slug == self._slug }
-      self.errors.add(:_slug, :taken)
-    end
-  end
-
   def highlighted_field_alias
     self.content_type.highlighted_field._alias.to_sym
   end
diff --git a/spec/models/content_instance_spec.rb b/spec/models/content_instance_spec.rb
index 9669ab61..1330f983 100644
--- a/spec/models/content_instance_spec.rb
+++ b/spec/models/content_instance_spec.rb
@@ -14,7 +14,6 @@ describe ContentInstance do
   end
 
   describe '#validation' do
-
     it 'is valid' do
       build_content.should be_valid
     end
@@ -32,14 +31,37 @@ describe ContentInstance do
       content.should_not be_valid
       content.errors[:_slug].should == ["can't be blank"]
     end
+  end
 
-    it 'has an unique permalink' do
-      build_content.save; @content_type = ContentType.find(@content_type._id)
-      content = build_content
-      content.should_not be_valid
-      content.errors[:_slug].should == ["is already taken"]
+  context 'setting the slug' do
+    before :each do
+      build_content(:_slug => 'dogs').tap(&:save!)._slug.should == 'dogs'
     end
 
+    it 'uses the given slug if it is unique' do
+      build_content(:_slug => 'monkeys').tap(&:save!)._slug.should == 'monkeys'
+      build_content(:_slug => 'cats-2').tap(&:save!)._slug.should == 'cats-2'
+    end
+
+    it 'appends a number to the end of the slug if it is not unique' do
+      build_content(:_slug => 'dogs').tap(&:save!)._slug.should == 'dogs-1'
+      build_content(:_slug => 'dogs').tap(&:save!)._slug.should == 'dogs-2'
+      build_content(:_slug => 'dogs-2').tap(&:save!)._slug.should == 'dogs-3'
+      build_content(:_slug => 'dogs-2').tap(&:save!)._slug.should == 'dogs-4'
+    end
+
+    it 'ignores the case of a slug' do
+      build_content(:_slug => 'dogs').tap(&:save!)._slug.should == 'dogs-1'
+      build_content(:_slug => 'DOGS').tap(&:save!)._slug.should == 'dogs-2'
+    end
+
+    it 'correctly handles slugs with multiple numbers' do
+      build_content(:_slug => 'fish-1-2').tap(&:save!)._slug.should == 'fish-1-2'
+      build_content(:_slug => 'fish-1-2').tap(&:save!)._slug.should == 'fish-1-3'
+
+      build_content(:_slug => 'fish-1-hi').tap(&:save!)._slug.should == 'fish-1-hi'
+      build_content(:_slug => 'fish-1-hi').tap(&:save!)._slug.should == 'fish-1-hi-1'
+    end
   end
 
   describe "#navigation" do
@@ -189,4 +211,4 @@ describe ContentInstance do
   def fake_bson_id(id)
     BSON::ObjectId(id.to_s.rjust(24, '0'))
   end
-end
\ No newline at end of file
+end