Antihypertensive and pharmacological properties of budralazine were examined in comparison with other antihypertensive drugs. Budralazine was orally effective against various types of hypertension in rats and it, like reserpine but unlike hydralazine, produced a much greater pressure reduction in hypertensive than in normotensive rats. The drug was similar to reserpine and alpha-methyldopa but not to hydralazine in showing a gradually progressive action. At equihypotensive oral doses, budralazine was less potent than hydralazine in producing tachycardia in unrestrained SHR. After long-term therapy, it effectively prevented the development of hypertension in SHR to almost the same extent as did hydralazine. Budralazine failed to produce diuresis in SHR at antihypertensive doses but antagonized isolated rabbit aortic contractions induced by vasoconstrictors and decreased femoral arterial resistance in dogs. Thus, the antihypertensive budralazine is characterized by the ability to produce vasodilator, non-diuretic and weak cardiac stimulant effects.