Exposure with response prevention and cognitive behavior therapy are widely recognized as effective treatments for obsessive-compulsive disorder. Unfortunately, many people with obsessive-compulsive disorder--particularly those living in rural areas--do not have access to therapists providing these treatments. Accordingly, we investigated the efficacy of telephone-administered cognitive behavior therapy for obsessive-compulsive disorder. Two open trials are reported, for a total of 33 people with obsessive-compulsive disorder (without major depression). The first trial consisted of 12 weeks on a waiting list followed by 12 weeks of treatment (delayed treatment). The second trial consisted of 12 weeks of immediate treatment. Obsessive-compulsive symptoms did not change during the waiting period. Symptoms declined from pre- to post-treatment, with gains maintained at 12-week follow-up. For the pooled sample our pre-to-post-treatment effect size was as large or larger than those obtained in other studies of reduced contact treatment, and similar to those of face-to-face exposure with response prevention. Our proportion of treatment dropouts tended to be lower than those of other reduced contact interventions. The results suggest that telephone-administered cognitive behavior therapy is effective and well-tolerated, at least for people with obsessive-compulsive disorder without major depression. It remains to be seen whether this treatment is safe and effective when comorbid major depression is present.