The influence of a new ACEI, Ramipril (R) on renal handling of UA was investigated. 13 hypertensives with normal renal function received either R (10 mg p.o.) or placebo (P). Arterial pressure (AP), GFR (Inulin clearance), Renal Plasma Flow (RPF, PAH clearance), UA urinary excretion (UAV) and fractional clearance (FeAU: UA clearance/GFR) were studied for seven hours after drug administration. GFR remained stable in all cases. R had no effect on sodium excretion rate. Compared to P, R significantly increased UAV by 25 p. 100, FeAU by 32 p. 100, RPF by 26.5 p. 100 and decreased mean arterial pressure (MAP) by 10 p. 100. ACE activity was maximally suppressed at 2 hours. More than 80 p. 100 of the maximal changes in UAU and FeAU were observed within the first two hours, while a progressive increase in RPF up to the fifth hour, and a progressive fall in MAP up to the fourth hour was evident. Except for PAM, all these changes were still present at the end of the study (seventh hour). In conclusion, Ramipril increases the fractional excretion of uric acid. This effect is observed independently of any change in sodium balance and preceeds by two to three hours the changes in renal hemodynamics. The simultaneous changes in FeAU and in ACE activity indicate that the effect on uric acid excretion is presumably due to the fall in angiotensin concentration.