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Patients who have received injections of colloidal thorium dioxide (Thorotrast) into the circulatory system constitute a pool from which information on the effects of long-term exposure to radiation can be obtained. The dosimetry of thorotrast is complicated by movement of the various daughter nuclides involved throughout the body. Radionuclide analysis of autopsy samples provides direct information on tissue concentrations of these nuclides which can be used for establishing the doses to organs of interest. This paper presents the results obtained on samples of tissues from two cases in the New England area. The first analyses, in each case, were performed about 24 hr post mortem. The concentrations of 228Ra, 228Th, 224Ra and 212Pb were determined by repetitive gamma examination over a period from 24 hr to 30 days. The samples were then dissolved and the concentrations of 232Th and 228Th determined by radiochemistry. The data indicate (1) that approximately 65% of 228Ra, the first daughter of 232Th is eliminated from the body, (2) that the parent 232Th is translocated to bone, and (3) that considerable quantities of 220Rn are liberated to blood. The effects of these findings on dosimetry are discussed. The autopsy findings are compared with whole body counting data, available on one of the patients.