A double-blind comparative study of doxazosin and prazosin in the treatment of essential hypertension. Two hundred sixty-six patients took part in a multicenter comparative study of doxazosin and prazosin. Both drugs produced a significant reduction (p less than 0.001) in blood pressure and no increase in heart rate. Blood pressure was considered "markedly decreased" or "decreased" in 70.8% of patients treated with doxazosin and 70.0% of patients treated with prazosin. No statistically significant between-group differences in antihypertensive efficacy were observed. Both doxazosin and prazosin were well tolerated; seven patients (5.6%) in each group had the therapy withdrawn. 