We have examined the possible renoprotective effect of felodipine 5 mg orally, given daily for 5 days before operation, in 29 patients undergoing elective infrarenal aortic surgery in a randomized, blinded and placebo-controlled study. Effective renal plasma flow (ERPF), glomerular filtration rate (GFR), urine output, fractional sodium clearance and plasma concentrations of angiotensin II, aldosterone, arginine vasopressin and atrial natriuretic peptide did not differ between the felodipine and placebo groups. ERPF and GFR were not reduced after operation in the placebo group. In the felodipine group, GFR was higher 24 h after operation compared with before operation. We conclude that increased GFR in the felodipine group, measured 24 h after operation, may indicate a beneficial effect of felodipine but in the present context this was not clinically important. Felodipine had no significant effect on vasoactive hormones.