diff --git a/lib/mongo/connection.rb b/lib/mongo/connection.rb
index 25f021a..67d60e0 100644
--- a/lib/mongo/connection.rb
+++ b/lib/mongo/connection.rb
@@ -448,7 +448,7 @@ module Mongo
       if num_received == 1 && (error = docs[0]['err'] || docs[0]['errmsg'])
         close if error == "not master"
         error = "wtimeout" if error == "timeout"
-        raise Mongo::OperationFailure, docs[0]['code'].to_s + ': ' + error
+        raise OperationFailure.new(docs[0]['code'].to_s + ': ' + error, docs[0]['code'], docs[0])
       end
 
       docs[0]
diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index d8e347a..971c418 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -122,10 +122,10 @@ module Mongo
         # connection. The next request will re-open on master server.
         if err == "not master"
           @connection.close
-          raise ConnectionFailure, err
+          raise ConnectionFailure.new(err, doc['code'], doc)
         end
 
-        raise OperationFailure, err
+        raise OperationFailure.new(err, doc['code'], doc)
       end
 
       if @transformer.nil?
@@ -175,7 +175,7 @@ module Mongo
       response = @db.command(command)
       return response['n'].to_i if Mongo::Support.ok?(response)
       return 0 if response['errmsg'] == "ns missing"
-      raise OperationFailure, "Count failed: #{response['errmsg']}"
+      raise OperationFailure.new("Count failed: #{response['errmsg']}", response['code'], response)
     end
 
     # Sort this cursor's results.
diff --git a/lib/mongo/db.rb b/lib/mongo/db.rb
index c358711..b25ecb9 100644
--- a/lib/mongo/db.rb
+++ b/lib/mongo/db.rb
@@ -123,13 +123,14 @@ module Mongo
       auth['user'] = username
       auth['nonce'] = nonce
       auth['key'] = Mongo::Support.auth_key(username, password, nonce)
-      if ok?(self.command(auth, :check_response => false, :socket => opts[:socket]))
+      if ok?(doc = self.command(auth, :check_response => false, :socket => opts[:socket]))
         if save_auth
           @connection.add_auth(@name, username, password)
         end
         true
       else
-        raise(Mongo::AuthenticationError, "Failed to authenticate user '#{username}' on db '#{self.name}'")
+        message = "Failed to authenticate user '#{username}' on db '#{self.name}'"
+        raise Mongo::AuthenticationError.new(message, doc['code'], doc)
       end
     end
 
@@ -506,7 +507,13 @@ module Mongo
       if result.nil?
         raise OperationFailure, "Database command '#{selector.keys.first}' failed: returned null."
       elsif (check_response && !ok?(result))
-        raise OperationFailure, "Database command '#{selector.keys.first}' failed: #{result.inspect}"
+        message = "Database command '#{selector.keys.first}' failed: ("
+        message << result.map do |key, value|
+          "#{key}: '#{value}'"
+        end.join('; ')
+        message << ').'
+        code = result['code'] || result['assertionCode']
+        raise OperationFailure.new(message, code, result)
       else
         result
       end
diff --git a/lib/mongo/exceptions.rb b/lib/mongo/exceptions.rb
index 875eeeb..2403cf9 100644
--- a/lib/mongo/exceptions.rb
+++ b/lib/mongo/exceptions.rb
@@ -22,7 +22,20 @@ module Mongo
   class MongoRubyError < StandardError; end
 
   # Raised when MongoDB itself has returned an error.
-  class MongoDBError < RuntimeError; end
+  class MongoDBError < RuntimeError
+
+     # @return The entire failed command's response object, if available.
+     attr_reader :result
+
+     # @return The failed command's error code, if availab.e
+     attr_reader :error_code
+
+     def initialize(message=nil, error_code=nil, result=nil)
+       @error_code = error_code
+       @result = result
+       super(message)
+     end
+  end
 
   # Raised when configuration options cause connections, queries, etc., to fail.
   class ConfigurationError < MongoRubyError; end
diff --git a/test/db_test.rb b/test/db_test.rb
index 2bb9108..910d2c8 100644
--- a/test/db_test.rb
+++ b/test/db_test.rb
@@ -206,8 +206,17 @@ class DBTest < Test::Unit::TestCase
 
   def test_check_command_response
     command = {:forceerror => 1}
-    assert_raise OperationFailure do 
+    raised = false
+    begin
       @@db.command(command)
+    rescue => ex
+      raised = true
+      assert ex.message.include?("forced error"),
+        "error message does not contain 'forced error'"
+      assert_equal 10038, ex.error_code
+      assert_equal 10038, ex.result['assertionCode']
+    ensure
+      assert raised, "No assertion raised!"
     end
   end