Despite the fact that majority of OCD patients responds to conventional treatments, about 40% remain symptomatic after appropriate trials with serotonin uptake inhibitors (SRIs) or behavioral therapy. A patient is considered treatment-resistant after failing to respond to three pharmacological trials with SRIs as well as to behavior therapy. When all somatic strategies have been tried, including augmentation with other medications, and the patient remains symptomatic, he or she is considered treatment refractory. The concepts of resistance and refractoriness are briefly revised, and the current augmentation strategies, as well as non-pharmacological approaches such as neurosurgery and transcranial magnetic stimulation, are addressed in this paper. Finally, issues of predictive response factors, pharmacogenetics, and the pathophysiology of resistant cases are suggested as targets for further researches.