The most common effective treatments for obsessive-compulsive disorder include clomipramine, fluoxetine, and exposure-based behavior therapy. A meta-analysis was conducted on the results from 25 appropriate treatment studies (1975-1991). All three treatments were significantly effective for most of the outcome variables (overall severity, anxiety, depression). Exposure was not significantly effective for reducing depressed mood. More treatment outcome studies are needed before a clearly superior treatment or combination of treatments can be statistically determined.