3-alpha-Phenyl-propyl-5-beta-diethylaminoethyl-1,2,3-oxadiazole (proxazole), a spasmolytic papaverine-like agent, was i.v. administered to 13 patients with chronic renal failure (mean creatinine clearance 46.4 ml/min/1.73 m2), but did not improve renal plasma flow (p-aminohippurate clearance) or glomerular filtration rate (inulin clearance), nor did this agent prevent or modify nor-adrenaline induced renal ischemia. The oral administration of 400 mg proxazole (5.2--6.5 mg/kg/day) for a period of at least 90 days did not improve renal function in 11 patients with chronic renal failure. It is concluded that both i.v. and p.o. administration of proxazole in the dosages used is ineffective in improving renal function in patients with chronic renal failure.