As no systemic data is available regarding the efficacy and safety of selective serotonin reuptake inhibitors (SSRI) in the treatment of OCD+BPD children, it calls for a preliminary open pilot treatment study to explore these issues as a logical first step that could lead to systematic randomized controlled trials in the future. SSRI's are the first line and most commonly used anti-OCD agents. It remains unknown, which of the standard SSRIs is least activating for youth with BPD. Fluoxetine along with fluvoxamine and sertraline are FDA approved for the treatment of OCD in children. Fluoxetine remains the most extensively studied SSRI in children. We will test the safety and efficacy of fluoxetine in children and adolescents with BPD and OCD.