Two patients suffering from severe obsessive-compulsive disorder which had proven refractory to clomipramine and/or phenelzine treatment were successfully treated with fluoxetine, a new drug with a strong serotonin uptake inhibiting action. Outcome of treatment was measured on psychometric tests including the Leyton Obsessive Inventory, Hopkins Symptom Checklist-90, Beck Depression Inventory, and daily self-reports of the duration and degree of discomfort of their most severe obsessions. The delay in responding to fluoxetine, the continuing improvement even after one year on the drug, and the prompt relapse with abrupt withdrawal of treatment were noted.