We studied 23 patients with renal functional deterioration after intravenous pyelography; 16 were nondiabetic. Nondiabetic patients at risk are often elderly and have preexisting renal disease. The course of acute renal failure is fairly characteristic; most patient recover, but some do not. Estimates suggest that the syndrome is not uncommon in susceptible nondiabetic subjects. Pyelography cannot be considered absolutely safe for this group, and alternative diagnostic procedures or caution with contrast dosage and patient preparation may be wise.