Antidepressant medication is considered the current standard for severe depression, and cognitive therapy is the most widely investigated psychosocial treatment for depression. However, not all patients want to take medication, and cognitive therapy has not demonstrated consistent efficacy across trials. Moreover, dismantling designs have suggested that behavioral components may account for the efficacy of cognitive therapy. The present study tested the efficacy of behavioral activation by comparing it with cognitive therapy and antidepressant medication in a randomized placebo-controlled design in adults with major depressive disorder (N = 241). In addition, it examined the importance of initial severity as a moderator of treatment outcome. Among more severely depressed patients, behavioral activation was comparable to antidepressant medication, and both significantly outperformed cognitive therapy. The implications of these findings for the evaluation of current treatment guidelines and dissemination are discussed. (Contains 2 tables, 4 figures, and 1 footnote.)