Obsessive-compulsive disorder (OCD) is a chronic, disabling, relapsing illness. It has been the subject of several recent national and international treatment guidelines that broadly recommend the use of selective serotonin reuptake inhibitors (SSRIs) or cognitive behaviour therapy (CBT) involving exposure and response prevention as preferred first line treatments. In this presentation I will critically review the evidence-base for pharmacological treatments, focussing on clinically relevant questions such as optimising dose and duration of SSRI, and evaluating the effect of treatment on health related disability and quality of life. For many individuals with OCD, SSRI or CBT only effect partial or even no treatment-response. Some evidence suggests adjunctive antipsychotic or high-dose SSRI therapy may be helpful, after SSRIs have failed. Other experimental treatments, either as a monotherapy (e.g. memantine) or adjunctive with SSRI (e.g. lamotrigine) have shown promise in preliminary trials and offer new treatment prospects for this frequently resistant disorder.