A small double-blind pilot study was carried out to assess whether captopril treatment in hypertension has a euphoriant effect. Eight patients were maintained on constant therapy of atenolol and bendrofluazide for at least 4 weeks before and throughout the study. Captopril 25 mg three times daily or matching placebo was administered double-blind for 6 weeks, with crossover to placebo or captopril from Weeks 7 to 12. Psychiatric assessment was made at Weeks 3, 6, 9, and 12. During the captopril phase, blood pressure was reduced, plasma angiotensin II lowered, and plasma renin raised. Mood was slightly, but significantly, lower during captopril administration; thus, there was no evidence of an euphoriant effect of captopril. This pilot trial also indicates the feasibility of the approach, and such studies of hypertensives under therapy should be usefully extended and refined.