The Provincial OCD Program at BC Children’s Hospital is recruiting greater Vancouver youth (7-19 years old) with obsessive compulsive disorder of moderate or higher severity to participate in a pilot trial of a graduated behavioural treatment approach. Youth will be randomized to receive treatment at home or at the hospital. In the first stage, youth receive an introductory session and two 3-hour exposure and response prevention (ERP) treatment sessions. Youth will be assessed for OCD recovery. Recovered youth enter follow-up. Still affected youth enter the second stage, where they can elect to receive up to four additional ERP sessions (one per week). In follow-up, youth will receive three 30 minute weekly calls and will be reassessed at one and six months following treatment.