Treatment of obsessive compulsive disorder has not changed a lot since 2000. Following a cautious assessment of the patient, using adequate scales, OCD patients require a step by step hierarchical treatment. A syndrome of low intensity (Yale-Brown Obsessive Compulsive Score [Y-BOCS] around 15) will be mainly treated by behavioural and cognitive therapy (BCT) especially exposition with prevention of response technique; for a more severe disorder, a drug treatment is required. Selective serotonin reuptake inhibitors (SSRI) are firstly recommended. They should be used in monotherapy with daily doses higher than those used for depression. Response is slow and usually delayed comparing to the alleviation of the depressive syndrome. A full response with disappearance of the symptoms is an exception. A good response to an antiobsessive treatment affords a 50% reduction of the intensity of OCD. Clomipramine may be slightly more effective than SSRI. Once, an improvement has been obtained, the drug titration should be kept for at least 18 to 24 months before attempting to discontinue medication. In case of non response, switching SSRI drug, combination with BCT may contribute to resolve the problem. In treatment refractory OCD, combination with either risperidone or olanzapine has shown some effective results in controlled trials. Finally, for several infrequent patients with a "malignant syndrome", functional neuro-surgery using deep brain stimulation might be a safe and hopeful therapeutic technique.