• We studied the course of depressive symptoms during an 18-month naturalistic follow-up period for outpatients with Major Depressive Disorder treated in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. The treatment phase consisted of 16 weeks of randomly assigned treatment with the following: cognitive behavior therapy, interpersonal therapy, imipramine hydrochloride plus clinical management (CM), or placebo plus CM. Follow-up assessments were conducted at 6,12, and 18 months after treatment. Of all patients entering treatment and having follow-up data, the percent who recovered (8 weeks of minimal or no symptoms following the end of treatment) and remained well during follow-up (no Major Depressive Disorder relapse) did not differ significantly among the four treatments: 30% (14/46) for those in the cognitive behavior therapy group, 26% (14/53) for those in the interpersonal therapy group, 19% (9/48) for those in the imipramine plus CM group, and 20% (10/51) for those in the placebo plus CM group. Among patients who had recovered, rates of Major Depressive Disorder relapse were 36% (8/22) for those in the cognitive behavior therapy group, 33% (7/21) for those in the interpersonal therapy group, 50% (9/18) for those in the imipramine plus CM group, and 33% (5/15) for those in the placebo plus CM group. The major finding of this study is that 16 weeks of these specific forms of treatment is insufficient for most patients to achieve full recovery and lasting remission. Future research should be directed at improving success rates of initial and maintenance treatments for depression.