The purpose of this study was to assess whether two-kidney, one clip (2K1C) renal hypertension can be induced in the marmoset. During the first 3-5 weeks after renal arterial clipping, blood pressure (BP) and plasma renin activity (PRA) increased in approximately one-third of the operated marmosets. However, within 10 weeks after clipping, BP and PRA had returned to control values. There was a significant positive correlation between BP and log PRA 3 and 5 weeks after the operation, but no correlation was observed at 10 weeks. In a selected group of marmosets with the highest values of BP (>140 mmHg; n=4), the converting enzyme inhibitor, enalapril (2 mg/kg s.c.) lowered BP by 58 ±7 (s.e.m.) mmHg when given 3 weeks after clipping. At 18 weeks the response to enalapril was only -17 ± 6 mmHg. These results demonstrate that unilateral renal arterial clipping in marmosets results in a transient renin-dependent hypertension. Marmosets in this initial hypertensive phase could be useful for investigating the antihypertensive effects of inhibitors of human renin.