This narrative review gathers together a range of international experts to critically appraise the existing trial-based evidence relating to the efficacy and tolerability of pharmacotherapy for obsessive compulsive disorder in adults. We discuss the diagnostic evaluation and clinical characteristics followed by treatment options suitable for the clinician working from primary through to specialist psychiatric care. Robust data supports the effectiveness of treatment with selective serotonin reuptake inhibitors (SSRIs) and clomipramine in the short-term and the longer-term treatment and for relapse prevention. Owing to better tolerability, SSRIs are acknowledged as the first-line pharmacological treatment of choice. For those patients for whom first line treatments have been ineffective, evidence supports the use of adjunctive antipsychotic medication, and some evidence supports the use of high-dose SSRIs. Novel compounds are also the subject of active investigation. Neurosurgical treatments, including ablative lesion neurosurgery and deep brain stimulation, are reserved for severely symptomatic individuals who have not experienced sustained response to both pharmacological and cognitive behavior therapies.