Dysfunction of the basal ganglia and frontal subcortical structures occurs in both obsessive-compulsive disorder and parkinsonism. Treatment of obsessive-compulsive disorder with parkinsonism is a therapeutic challenge, especially in old age as selective serotonin reuptake inhibitors may aggravate motor symptoms and worsen clinical conditions. The authors present a series of patients with late onset obsessive-compulsive disorder demonstrating improvement in obsessive-compulsive disorder as well as parkinsonian signs.