We studied renal, hormonal and cardiovascular effects of ANF 102-126 (WY 47987) in seven patients with chronic renal failure (serum creatinine 25-68 mg/l) and in four normal volunteers. ANF or placebo bolus injections were given at 1, 2, and 3 micrograms/kg i.v. (each dose on separate days). As compared to placebo, ANF did not induce changes of renal excretory parameters, of plasma renin and aldosterone or of blood pressure and heart rate in patients. In healthy volunteers, however, the same dose of ANF increased urinary excretion of sodium, potassium, calcium, chloride and phosphorus as well as water, and creatinine clearances, and decreased plasma aldosterone. The data suggest blunted effectiveness of ANF bolus injections in patients with renal insufficiency.