The bioavailability of 205Bi from various 205Bi-labelled pharmaceutical oral bismuth preparations was studied in rats. The intestinal absorption, calculated from 205Bi whole body retention and accumulated 205Bi urinary excretion, was small in general, but significantly higher (0.26-0.33% of dose) from oral bismuth citrates (basic bismuth citrate, colloidal bismuth subcitrate) as compared to basic bismuth nitrate, salicylate, gallate, and bismuth aluminate (0.04-0.11% of dose). After oral administration, the retained bismuth was mainly accumulated in the kidney, followed by bone, red blood cells and the lung. The whole body retention, faecal and urinary excretions of 205Bi were described by a three-compartment model. Biological 205Bi half-lives of 10, 36 and 295 h were derived in rats.