Diuresis renography was performed twice at an interval of one week in 13 uraemic patients without hydronephrosis. In five of the patients, the 51Cr-EDTA clearance was below 10 ml/min x 1.73 m2 for the individual kidney, in eight of the patients between 10 and 25. During the renographies, respectively, 0.5 and 7.5 mg/kg of frusemide was given I.V. at 20 min. Compared with the data from eight normal control patients, the effect of frusemide on the renography curve was very poor and varied much in both groups. Our results suggest that diuresis renography gives no conclusive information about the upper urinary tract in kidneys with a 51Cr-EDTA clearance below 25 ml/min x 1.73 m2, even when the dose of frusemide is increased to 7.5 mg/kg.