Eleven cases of chrysiasis have been studied ultrastructurally and by electron probe microanalysis. Tissue samples were examined both with and without osmium and uranyl acetate staining. There was a significant morphological difference in the appearances of the gold deposits within aurosomes between the two groups. The untreated group showed finely granular deposits, often arranged in a linear fashion. Aurosomes from samples treated with osmium and uranyl acetate showed more electron-dense deposits and star-like formations. We propose that treatment of the tissue with osmium and uranyl acetate causes a change in the electron microscopic appearance of aurosomes, including the formation of the characteristic star-like aurosomes.