Previously thought of as merely an interesting syndrome, obsessive-compulsive disorder is now estimated to afflict 1%-2% of the world's population. Over the past decade extensive research into the epidemiology, aetiology, pathophysiology and pharmacological treatment of this condition has greatly improved its prognosis. This is largely due to the development of the serotonergic group of antidepressants, the selective serotonin reuptake inhibitors (SSRIs), which have consistently demonstrated antiobsessional properties. Monoamine oxidase inhibitors (MAOIs) and lithium have also contributed to the amelioration of symptoms in some patients. Other pharmacological treatment, often prescribed in combination with the SSRIs, include the antipsychotic drugs, benzodiazepines, and anticonvulsants.