The accumulation of arsenic (7440382) (As) compounds was studied in human tissues. The adrenal gland, aorta, cerebellum, cerebrum, kidney, liver, lung, muscle, pancreas, skin, and spleen obtained from autopsied cadavers of 13 males and 10 females, 36 to 79 years of age, were assayed for As compounds. The As concentrations were determined by arsine generator flameless atomic absorption spectrophotometry. The highest mean total As concentration of 551 nanograms per gram (ng/g) occurred in the aorta. The As content of the other tissues in ng/g were: adrenal gland, 327; cerebellum, 132; cerebrum, 76.3; kidney, 129; liver, 129; lung, 104;, muscle, 106; pancreas, 154; skin, 153; and spleen, 101. There were four chemical species of As detected: arsenite (As(III)), arsenate (As(V)), methylarsonic-acid (MAA), and dimethylarsinic-acid (DMAA). As(V) was the most predominant of the chemical species, accounting for 7.20 percent of the As. As(V) and As(III) were found in all tissues and organs. MAA was found only in the kidney and liver. DMAA was found in small amounts in all organs except the cerebellum and cerebrum. There were no significant sexual differences in the tissue and organ distributions of the compounds.