Cognitive therapy for OCD is an empirically validated alternative to the more widely used and validated behavioral therapy for OCD. The cognitive approach is based on the premise that belief systems contribute importantly to the development and maintenance of all types of OCD. By identifying and challenging maladaptive thoughts, beliefs, and core beliefs, patients can improve significantly and maintain their gains over time. This approach is demonstrated in detail with the case of Caroline, a 51-year-old woman with contamination obsessions. (Contains 2 figures.)