Sulphonyle ureas used in the oral treatment of diabetes occupy albumen-binding capacity. Hepatotropic contrast media therefore have difficulty with protein binding and renal excretion is increased. The proportion excreted through the kidneys has been determined in 50 diabetic patients on oral treatment. Demonstration of contrast in the urine was done radiologically, qualitative measurements by a subtraction method. As a control, the same group of patients were examined, having been taken off suphonyle ureas, as well as a group of 50 diabetic patients treated with insulin. While under medication, heteroptropic excretion rose on average to 55% and in some cases to 80%. This results in definite reduction of contrast filling of the biliary tree, occasionally to the extent of preventing a diagnosis. Displacement of sulphonyle urea by contrast was not observed.