Exposure and Response (ritual) Prevention (EX/RP) for obsessive-compulsive disorder (OCD) is a behaviorally based treatment that is the most effective treatment available for most patients with OCD. In this paper, we will provide a brief description of OCD and outcome data on EX/RP, followed by discussion of the procedures and techniques involved in EX/RP which include imaginal exposure, in vivo exposure, and ritual prevention. ********** OCD Obsessions are intrusive thoughts, images, or impulses that keep coming back to people and that do not make sense. Some common obsessions include fear of contamination, fear of harm to self or others, fear of sin or immorality (also known as scrupulosity), intrusive sexual thoughts, a need for symmetry or exactness, and fear of losing things or throwing things away. Compulsions are behaviors or acts which people feel driven to perform and have difficulty resisting. Common compulsions include washing, checking, reviewing, hoarding, reassurance seeking, and mental neutralizing. Compulsions, whether overt behaviors or are meant to alleviate the distress brought on by obsessional thoughts and/or to prevent bad things from happening (e.g., patients with contamination obsessions wash their hands to prevent themselves from getting ill). Most patients tend to have more than one type of obsession or compulsion. When patients engage in an hour or more of obsessions or compulsions in a day, or if they are distressed or impaired due to these symptoms, then the patient is considered to have OCD. EX/RP Effective treatment for OCD must involve both exposure and ritual prevention. Exposure involves confronting situations, objects, and thoughts that evoke anxiety or distress because they are unrealistically associated with danger. Response (ritual) prevention is conceptualized as blocking avoidance or escape from feared situations. By encouraging the individual to remain in the feared situation without any avoidance behaviors, EX/RP affords patients the opportunity to learn that their fears are unrealistic. It is essential that clinicians and patients understand why it is so important to do exposure and ritual prevention together. Many patients would not mind confronting a feared stimulus (e.g., touching something contaminated) if they could then engage in rituals (e.g., handwashing). Rachman and his colleagues (see Rachman & Hodgson, 1980) showed that exposure to cues that trigger obsessions increase anxiety and discomfort and that ritualistic behavior led to a decrease in anxiety and discomfort. When patients were exposed to obsessional cues, but were prevented from engaging in rituals, anxiety and discomfort decreased over time. When patients were then exposed to their obsessional cues again, the urge to ritualize had decreased as compared to the previous trial. This decrease in urge to ritualize did not occur if patients continued to engage in rituals in response to obsessional cues. Foa and colleagues (1984) showed further evidence for the importance of using both exposure and ritual prevention in the treatment of OCD. In this study, patients with OCD were randomly assigned to receive either exposure alone, ritual prevention alone, or combined EX/RP. The component treatments seemed to have unique effects on OCD symptoms--ritual prevention led to reduction in compulsions and exposure led to reduction in the anxiety response to feared stimuli. Not surprisingly then, the combined treatment was found to be superior to the component treatments, with patients in this group showing the greatest reductions in both anxiety and compulsions. EX/RP treatment programs have gained empirical support, with both adults (Foa, Liebowitz, & colleagues, in preparation) and children (deHaan et al., 1998) treated with EX/RP showing more improvement in OCD symptoms than those treated with medication. …