A double-blind comparative study of clomipramine and diazepam was carried out in patients suffering from phobic and obsessional disorders. Nineteen doctors submitted 58 patients. Seventeen patients withdrew from the trial, twelve because of side-effects. Forty-one patients completed the trial and of these 14 were on clomipramine and 27 were taking diazepam. Patients were assessed for phobias, obsessions, general psychiatric symptoms and side-effects and each was rated on a special symptom inventory at 0, 2, 4 and 6 weeks of treatment. A General Health Questionnaire and Burns Questionnaire was completed for each patient at the beginning and end of the study. General level of anxiety for diffuse phobic anxiety and situational anxiety for illness and death fears responded better to clomipramine than to diazepam. Global assessment showed significantly more progress on clomipramine than diazepam between weeks 4 and 6.