The purpose of this study was to determine the effectiveness of exposure and response prevention by self-treatment method on the reduction of obsessive-compulsive symptoms in out-patients who referred to psychiatric and psychological service centers in Isfahan. Therefore 20 patients with obsessive-compulsive disorder who were diagnosed on the basis of clinical interviewed and they did not have a major depressive disorder and personality disorders were randomly selected and assigned to two groups: training and control groups. The training group received a self-treatment manual booklet prepared by the experimenter. This booklet contained practical instructions and homework that were based on exposure and response prevention treatment method. The length of treatment was 6 weeks and the subjects were asked to give weekly reports of their progress to the experimenter by phone. The subjects in control group were assigned to waiting list. Maudsley Obsessive-Compulsive Inventory were administered to all subjects as the pre- test post- test and follow-up. The results of analysis of covariance revealed that the training group showed significantly lower score than the control group on the post-test and on the one-month follow-up of maudsley obsessive-Compulsive Inventory(P < 0.001). It is concluded that exposure and response prevention by self-treatment can be used as an effective method in treatment of obsessive-compulsive disorders.