Twenty-nine patients with obsessive-compulsive disorder as diagnosed in accordance with the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised; American Psychiatric Association, 1987) who did not have overt compulsive rituals were randomly assigned to treatment and waiting-list conditions. Patients in the treatment condition received cognitive-behavioral therapy consisting of a detailed explanation of the occurrence and maintenance of obsessive thoughts, exposure to obsessive thoughts, response prevention of all neutralizing strategies, cognitive restructuring, and relapse prevention. Compared with waiting-list patients, treated patients improved significantly on measures of severity of obsessions, current functioning, self-report obsessive-compulsive symptoms, and anxiety. When waiting-list patients were subsequently treated, the combined group improved on all outcome measures. Treatment gains were maintained at 6-month follow-up. Results indicate that cognitive-behavioral therapy is effective in the treatment of patients with obsessive thoughts, a group that has often been considered resistant to treatment.