The obsessive-compulsive disorder (OCD) is a chronic and disabling neurotic disorder. Unit recently the information about the incidence, etiology and treatment of this disorder was based on researches done on relatively small samples. In the past few years, owing to a number of studies done on different populations, public knowledge about this disorder has been increased and patients have been persuaded to seek treamtnet by going to psychiatric centers.

In this article the most up to data studies on various aspects of OCD are reviewd. These include:

1- Epidemiology and differential diagnosis of OCD.

2- OCD in childhood.

3- Serotonin hypotheisi in the etiology of OCD.

4- Pharmacological studies in OCD.

5- Integrative approach to the treatment of OCD.