This paper reviews the evidence-based literature concerning the efficacy and effectiveness of cognitive behavior therapy (CBT), drug treatment and their combination for obsessive compulsive disorder (OCD). After a brief outline of the seminal studies, the state of the art is presented with reference to the consensual recommendations proposed in the last 10 years. Management of OCD rests on potent selective serotonin reuptake inhibitors and CBT, used separately, sequentially, or concurrently. A hierarchical model for clinical decision-making is reported. With greater severity of OCD, it is recommended to add medications. However, the response rate is still too low in many patients, and some patients remain refractory to any kind of treatment. This stresses the importance of joint efforts of psychological and biological teams to develop new treatments.