The effects of bromocriptine (BRC; 20 mg X kg-1, b.i.d., orally) on genetic hypertension development (GHD), cardiovascular hemodynamics, regional vascular reactivity to vasopressor agents and biological parameters have been investigated in spontaneously hypertensive rats (SHRs) treated from their 4th to 20th weeks of age. BRC only partially opposed GHD and this was due to a limitation of the progressive increase in peripheral resistance which normally develops in SHRs with ageing since simultaneously cardiac index was not modified. Renal blood flow was increased and renal and mesenteric vascular responsiveness to norepinephrine was reduced. BRC almost completely suppressed prolactin plasma levels and slightly reduced epinephrine and norepinephrine plasma levels. Plasma Na+ and urinary volume and ADH values were not modified. The discrepancy between the favourable antihypertensive profile of BRC and its limited preventive effects against GHD remains to be elucidated.