To estimate radiation dose of Tc-99m and In-III complexes with diethylenetriomine pentacetic acid [DTPA] a glomerular agent organ assays and excretion measurements were conducted in dogs at various time intervals up to 24 h, and the results compared with available human data. The peak concentration of the Tc-99m complex, at 3 min after injection, was 5% of the administered dose for 1 kidney, 3.5% for the liver and 3.5% for the small bowel. No organ system except the urinary tract reached a concentration higher than in blood for several hours after the injection. The biliary excretion of these agents was extremely low and their elimination in the feces was negligible. In man the residual 4-5% of an administered dose not eliminated in the urine by 24 h is widely distributed in various tissues. The distribution of the In-111 complex is similar but not identical to the Tc-99m complex.