diff --git a/lib/mongo/collection.rb b/lib/mongo/collection.rb
index 4411458..33d330b 100644
--- a/lib/mongo/collection.rb
+++ b/lib/mongo/collection.rb
@@ -34,6 +34,11 @@ module Mongo
     #   for insert, update, and remove method called on this Collection instance. If no
     #   value is provided, the default value set on this instance's DB will be used. This
     #   default can be overridden for any invocation of insert, update, or remove.
+    # @option options [:primary, :secondary] :read The default read preference for queries
+    #   initiates from this connection object. If +:secondary+ is chosen, reads will be sent
+    #   to one of the closest available secondary nodes. If a secondary node cannot be located, the
+    #   read will be sent to the primary. If this option is left unspecified, the value of the read
+    #   preference for this collection's associated Mongo::DB object will be used.
     #
     # @raise [InvalidNSName]
     #   if collection name is empty, contains '$', or starts or ends with '.'
@@ -84,8 +89,12 @@ module Mongo
       @cache = Hash.new(0)
       unless pk_factory
         @safe = opts.fetch(:safe, @db.safe)
-        @read = opts.fetch(:read, @db.read_preference)
-        @read_preference = @read.is_a?(Hash) ? @read.dup : @read
+        if value = opts[:read]
+          Mongo::Support.validate_read_preference(value)
+        else
+          value = @db.read_preference
+        end
+        @read_preference = value.is_a?(Hash) ? value.dup : value
       end
       @pk_factory = pk_factory || opts[:pk] || BSON::ObjectId
       @hint = nil
@@ -157,6 +166,11 @@ module Mongo
     #   you can cut down on network traffic and decoding time. If using a Hash, keys should be field
     #   names and values should be either 1 or 0, depending on whether you want to include or exclude
     #   the given field.
+    # @option opts [:primary, :secondary] :read The default read preference for queries
+    #   initiates from this connection object. If +:secondary+ is chosen, reads will be sent
+    #   to one of the closest available secondary nodes. If a secondary node cannot be located, the
+    #   read will be sent to the primary. If this option is left unspecified, the value of the read
+    #   preference for this Collection object will be used.
     # @option opts [Integer] :skip number of documents to skip from the beginning of the result set
     # @option opts [Integer] :limit maximum number of documents to return
     # @option opts [Array]   :sort an array of [key, direction] pairs to sort by. Direction should
diff --git a/lib/mongo/connection.rb b/lib/mongo/connection.rb
index 4b5b4f8..f17abe9 100644
--- a/lib/mongo/connection.rb
+++ b/lib/mongo/connection.rb
@@ -685,6 +685,7 @@ module Mongo
       @connect_timeout = opts[:connect_timeout] || nil
 
       # Mutex for synchronizing pool access
+      # TODO: remove this.
       @connection_mutex = Mutex.new
 
       # Global safe option. This is false by default.
diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index 971c418..f592759 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -70,8 +70,12 @@ module Mongo
       @query_run    = false
 
       @transformer = opts[:transformer]
-      read         = opts[:read] || collection.read_preference
-      @read_preference = read.is_a?(Hash) ? read.dup : read
+      if value = opts[:read]
+        Mongo::Support.validate_read_preference(value)
+      else
+        value = collection.read_preference
+      end
+      @read_preference = value.is_a?(Hash) ? value.dup : value
       batch_size(opts[:batch_size] || 0)
 
       @full_collection_name = "#{@collection.db.name}.#{@collection.name}"
diff --git a/lib/mongo/db.rb b/lib/mongo/db.rb
index b25ecb9..e82c2f7 100644
--- a/lib/mongo/db.rb
+++ b/lib/mongo/db.rb
@@ -82,8 +82,12 @@ module Mongo
       @strict     = opts[:strict]
       @pk_factory = opts[:pk]
       @safe       = opts.fetch(:safe, @connection.safe)
-      read = opts.fetch(:read, @connection.read_preference)
-      @read_preference = read.is_a?(Hash) ? read.dup : read
+      if value = opts[:read]
+        Mongo::Support.validate_read_preference(value)
+      else
+        value = @connection.read_preference
+      end
+      @read_preference = value.is_a?(Hash) ? value.dup : value
       @cache_time = opts[:cache_time] || 300 #5 minutes.
     end
 
diff --git a/lib/mongo/repl_set_connection.rb b/lib/mongo/repl_set_connection.rb
index f016d13..ef7f50f 100644
--- a/lib/mongo/repl_set_connection.rb
+++ b/lib/mongo/repl_set_connection.rb
@@ -41,8 +41,10 @@ module Mongo
     #   propogated to DB objects instantiated off of this Connection. This
     #   default can be overridden upon instantiation of any DB by explicity setting a :safe value
     #   on initialization.
-    # @option options [Boolean] :read_secondary(false) If true, a random secondary node will be chosen,
-    #   and all reads will be directed to that node.
+    # @option options [:primary, :secondary] :read (:primary) The default read preference for Mongo::DB
+    #   objects created from this connection object. If +:secondary+ is chosen, reads will be sent
+    #   to one of the closest available secondary nodes. If a secondary node cannot be located, the
+    #   read will be sent to the primary.
     # @option options [Logger, #debug] :logger (nil) Logger instance to receive driver operation log.
     # @option options [Integer] :pool_size (1) The maximum number of socket connections allowed per
     #   connection pool. Note: this setting is relevant only for multi-threaded applications.
@@ -125,6 +127,7 @@ module Mongo
         @read = :secondary
       else
         @read = opts.fetch(:read, :primary)
+        Mongo::Support.validate_read_preference(@read)
       end
 
       @connected = false
diff --git a/lib/mongo/util/support.rb b/lib/mongo/util/support.rb
index 2f56b18..7a63643 100644
--- a/lib/mongo/util/support.rb
+++ b/lib/mongo/util/support.rb
@@ -44,7 +44,6 @@ module Mongo
       Digest::MD5.hexdigest("#{username}:mongo:#{plaintext}")
     end
 
-
     def validate_db_name(db_name)
       unless [String, Symbol].include?(db_name.class)
         raise TypeError, "db_name must be a string or symbol"
@@ -59,6 +58,15 @@ module Mongo
       db_name
     end
 
+    def validate_read_preference(value)
+      if [:primary, :secondary, nil].include?(value)
+        return true
+      else
+        raise MongoArgumentError, "#{value} is not a valid read preference. " +
+          "Please specify either :primary or :secondary."
+      end
+    end
+
     def format_order_clause(order)
       case order
         when String, Symbol then string_as_sort_parameters(order)
diff --git a/test/replica_sets/read_preference_test.rb b/test/replica_sets/read_preference_test.rb
index 59952e9..59a9b3c 100644
--- a/test/replica_sets/read_preference_test.rb
+++ b/test/replica_sets/read_preference_test.rb
@@ -1,41 +1,43 @@
 $:.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
 require './test/replica_sets/rs_test_helper'
 
+# TODO: enable this once we enable reads from tags.
 class ReadPreferenceTest < Test::Unit::TestCase
   include Mongo
 
-  def setup
-    @conn = ReplSetConnection.new([RS.host, RS.ports[0], RS.host, RS.ports[1]], :read => :secondary, :pool_size => 50)
-    @db = @conn.db(MONGO_TEST_DB)
-    @db.drop_collection("test-sets")
-  end
+  #def setup
+  #  @conn = ReplSetConnection.new([RS.host, RS.ports[0], RS.host, RS.ports[1]], :read => :secondary, :pool_size => 50)
+  #  @db = @conn.db(MONGO_TEST_DB)
+  #  @db.drop_collection("test-sets")
+  #end
 
-  def test_query_tagged
-    col = @db['mongo-test']
+  # TODO: enable this once we enable reads from tags.
+  # def test_query_tagged
+  #   col = @db['mongo-test']
 
-    col.insert({:a => 1}, :safe => {:w => 3})
-    col.find_one({}, :read => {:db => "main"})
-    col.find_one({}, :read => {:dc => "ny"})
-    col.find_one({}, :read => {:dc => "sf"})
+  #   col.insert({:a => 1}, :safe => {:w => 3})
+  #   col.find_one({}, :read => {:db => "main"})
+  #   col.find_one({}, :read => {:dc => "ny"})
+  #   col.find_one({}, :read => {:dc => "sf"})
 
-    assert_raise Mongo::NodeWithTagsNotFound do
-      col.find_one({}, :read => {:foo => "bar"})
-    end
+  #   assert_raise Mongo::NodeWithTagsNotFound do
+  #     col.find_one({}, :read => {:foo => "bar"})
+  #   end
 
-    threads = []
-    100.times do
-      threads << Thread.new do
-        col.find_one({}, :read => {:dc => "sf"})
-      end
-    end
+  #   threads = []
+  #   100.times do
+  #     threads << Thread.new do
+  #       col.find_one({}, :read => {:dc => "sf"})
+  #     end
+  #   end
 
-    threads.each {|t| t.join }
+  #   threads.each {|t| t.join }
 
-    col.remove
-  end
+  #   col.remove
+  # end
 
-  def teardown
-    RS.restart_killed_nodes
-  end
+  #def teardown
+  #  RS.restart_killed_nodes
+  #end
 
 end
diff --git a/test/unit/read_test.rb b/test/unit/read_test.rb
index 40ce098..0a34668 100644
--- a/test/unit/read_test.rb
+++ b/test/unit/read_test.rb
@@ -87,11 +87,14 @@ class ReadTest < Test::Unit::TestCase
       end
 
       should "allow override alternate value on query" do
-        @con.expects(:receive_message).with do |o, m, l, s, c, r|
-          tags = {:dc => "ny"}
-        end.returns([[], 0, 0])
+        # TODO: enable this test once we enable reading from tags.
+        # @con.expects(:receive_message).with do |o, m, l, s, c, r|
+        #   tags = {:dc => "ny"}
+        # end.returns([[], 0, 0])
 
-        @col.find_one({:a => 1}, :read => {:dc => "ny"})
+        assert_raise MongoArgumentError do
+          @col.find_one({:a => 1}, :read => {:dc => "ny"})
+        end
       end
     end
   end