Proponents of cognitive therapy have striven to establish this approach as a mature system of psychotherapy for over 3 decades. The theoretical formulations have been enriched by clinical extrapolations from the neopsychoanalysts and experimental findings from cognitive psychology. The therapeutic strategies and techniques have been refined as a result of interaction with behavior therapy, which also influenced the emphasis on empirical testing of the theoretical formulations and the therapeutic applications. Outcome trials have demonstrated efficacy in a number of common disorders. New emphasis on the crucial importance of specific formulations (especially dysfunctional beliefs) has provided important clues to the treatment of a large number of other disorders. I conclude that cognitive therapy has fulfilled the criteria of a system of psychotherapy by providing a coherent, testable theory of personality, psychopathology, and therapeutic change; a teachable, testable set of therapeutic principles, strategies, and techniques that articulate with the theory; and a body of clinical and empirical data that support the theory and the efficacy of the theory.