Renal uptake of 99m Tc DMSA was used to evaluate the renal function of 16 healthy subjects (controls) and 115 patients with various urinary tract diseases. Scintigraphic examination was carried out 6 hours after an intravenous injection of the product. In the 16 controls Tc DMSA uptake was 25.7 +/- 2.48% in the right kidney and 24.4 +/- 2.86% in the left kidney. In 36 patients with one single hypertrophied kidney, there was a correlation (r = 0.850) between creatinine clearance and Tc DMSA uptake, which was higher than in normal subjects (39.23 +/- 9.9%). In the group of 68 patients with unilateral (31) or bilateral (37) renal disease, a significant correlation (r = 0,725) was observed between kidney-to-kidney ratios of urea clearance and Tc DMSA uptake, so that renal impairment could be quantified. Quantitative scintigraphy did not appear to be of assistance in the remaining 11 patients with obstructive uropathy, as it overestimated renal function. The results obtained with 99 m Tc DMSA scintigraphy should be helpful in choosing between nephrectomy and conservative surgery and in assessing the degree of compensatory hypertrophy in single kidneys.