The effect of cadmium chloride on hepatocellular apoptosis in rats was studied in vivo at the doses of 5, 10 and 20 mumol/kg by using TUNEL (TdT-mediated dUTP Nick End Labelling), DNA ladder electrophoresis and flow cytometry. The results showed that TUNEL-positive cells could be detected in cadmium-treated rat liver cells. DNA fragmentation (ladder pattern) in cadmium-treated liver cells could be displayed by agarose gel electrophoresis. The rates of apoptotic cells in the liver of cadmium-treated rats at these doses were higher than those of control rats significantly. It was suggested that cadmium chloride could induce hepatocellular apoptosis of rats at certain doses in vivo.