This article summarizes results of all pharmacotherapy trials for obsessive-compulsive disorder (OCD) published from 2006 to 2008 as well as studies on markers for predicting response to treatment and neurobiological changes induced by pharmacotherapy. Results show that recent developments in the treatment of OCD have been modest and primarily involve evidence for the efficacy of escitalopram and other selective serotonin reuptake inhibitors (SSRIs); augmentation with antipsychotics in treatment-refractory patients and combination treatment with D-cycloserine and cognitive-behavioral therapy has also been effective. The efficacy of serotonin-norepinephrine reuptake inhibitors remains inconclusive. Studies on markers of clinical response have shown inconsistent results, however, duration and severity of OCD and the presence of comorbidities can often identify patients at risk for nonresponse. Lastly, successful treatment with an SSRI results in both serotonergic and dopaminergic changes, but more research is necessary in order to define the biological characteristics of responders and nonresponders.