Metacognitive theory and therapy views the persistence of negative beliefs and thoughts as a result of metacognitions controlling cognition. This paper describes, with reference to the treatment of generalized anxiety disorder (GAD) and social phobia, how metacognition contributes to cognitive stability and to change. Metacognitive therapy offers a level of formulation and intervention that does not focus predominantly on challenging the content of negative thoughts and beliefs that are emphasized in traditional cognitive therapy. The focus of treatment in GAD is on erroneous beliefs about worry and unhelpful mental regulation strategies. In treating social phobia, a greater emphasis is placed on modifying attention and worry processes and on configuring processing during and after behavioral experiments. (Contains 2 figures.)