This article reviews the theoretical and empirical literature associated with the mediators and moderators of change in cognitive therapy (CT) of depression. Covariation between change in cognition and change in depression, specific effects for cognitive versus behavioral components of CT, specific effects for CT versus other treatments, moderating influence of nonspecific and technical aspects of the therapeutic environment, and moderating influence of client characteristics are reviewed. The clinical implications of prior research and suggestions for future research on identifying the critical ingredients of change in CT of depression are discussed.