The study design allows for a novel, well-powered and potentially landmark study on the impact of exercise on obsessive-compulsive symptom severity and cognitive functioning in OCD, both as a stand-alone treatment and when augmenting CBT. If this study can demonstrate that a short aerobic exercise program of 12 weeks duration can confer significant clinical gains for those suffering with OCD, then it could easily be translated into highly accessible, routine clinical care. Further, demonstration of improvement in OCD-associated cognitive dysfunction, given the refractory nature of the illness, would provide another avenue into the long-term enhancement of outcomes for this chronically affected population.