The liver and kidney tolerance of iopromide 370 in comparison to that of sodium meglumine diatrizoate 370 or iopamidol 370 in doses of 2 ml/kg body weight was examined in two controlled double-blind studies with intravenous digital subtraction angiography on the basis of enzyme assays in serum and urine. In patients with normal kidney function no changes were observed in the levels of the liver enzymes GPT, GOT, and gamma glutamyl transpeptidase (GGT) serum up to 72 hours after injection of iopromide or sodium meglumine diatrizoate. Among the kidney-specific enzymes, the excretion of GGT in urine increased after injection of iopromide and iopamidol. The maximum increase of GGT excretion was, however, statistically significantly lower in the group treated with iopromide than in the iopamidol group. Within 72 hours, the activities had been returned to the initial values in both groups.