We studied the roles of the sympathoadrenal system and endogenous opiate in the antihypertensive effects of supplementation of dietary taurine, a sulfur amino acid. in deoxycorticosterone acetate (DOCA)-salt rats. Supplementation of 1% taurine in drinking water for 2 weeks was found to prevent the increase in systolic blood pressure of DOCA-salt rats (116±2 vs 138±mmHg, p<0.01). but failed to effect the systolic blood pressure of vehicle-treated control rats (115±2 vs 112±3mmHg). taurine supplementation restored to normal in-creased plasma norepinephrine (326±32 vs 531±67pg/ml, p<0.01) and epinephrine (204±19 vs 304±43pg/ml. p<0.05) concentrations in DOCA-salt rats, but had no effect on norepinephrine (346±23 vs 338±33pg/ml) or epinephrine (198±17 vs 224±26pg/ml) concentrations in control rats. Accordingly, the increased epinephrine content in the adrenals of DOCA-salt rats was normalized with the supplementation of taurine, associated with a markedly in-creased adrenal taurine content. In conscious rats, moreover, intraperitoneal injection of naloxone (2mg/kg). a specific opiate antagonist, increased systolic blood pressure only in taurine-supplemented DOCA-salt rats. Evidence presented suggests. therefore, that both the suppression of the increased sympathoadrenal activity and the activation of endogenous opiate might contribute to the antihypertensive effect of taurine in DOCA-salt rats.