Losses of chromium, iron, zinc and cadmium during ashing were studied using tissues that contained endogenously incorporated radioisotopes. No losses on drying at 110 °C and no volatility losses were detected for any of the elements at temperatures below 600 °C. Chromium was lost from blood but not from liver samples heated at 700 °C. Losses as insoluble material on the crucible surfaces were more significant. Up to 42% of the isotope was retained on the dish after dissolution with acid, the amount depending on the ashing temperature, crucible material and surface condition. No evidence for the formation of volatile compounds from the endogenously incorporated isotope was found.