The time course of distribution of tin in the adult rat was determined in brain, liver kidney, heart, and blood following single ip administrations of trimethyltin hydroxide (TMT) and triethyltin bromide (TET). Adult Long-Evans rats were killed 1 hr, 4 hr, 12 hr, 24 hr, 5 days, 10 days, or 22 days following injection of TMT and TET (N=6/time), and tissues were analyzed for total tin by atomic absorbance spectroscopy. TET exposure resulted in higher tin levels in brain, liver and kidney tissues, while the two trialkyltins resulted in approximately equal tin levels in the heart and blood. Rates of elimination of tin (expressed as elimination rate constants, Kel) were greater in all tissues following TET exposure than following TMT exposure. The concentration of tin in the brain 12 hr after TMT exposure was 4.4, 8.5, and 12.7 ng tin/mg protein for dosages of 3.0, 6.0, and 9.0 mg/kg, respectively. Tin was evenly distributed across the cerebellum, medula-pons, hypothalamus, hippocampus, and striatum following TMT exposure.