Deoxynivalenol (DON) is one of the major mycotoxic contaminants of grains, which causes reduced weight gain in pigs. The cytotoxicity of DON to porcine hepatocytes was examined in this study. DON was added at the final concentration of 100, 10, 1, 0.1 or 0.01 microg/ml to the medium of primary cultured hepatocytes. Cell death of the hepatocytes was observed in DON 100 and 10 microg/ml groups from 6 h after the addition, and in DON 100, 10, 1 and 0.1 microg/ml groups at 24 h in a dose-dependent manner. The dead hepatocytes showed chromatin condensation and fragmentation of the nuclei, which are considered characteristic morphological changes of apoptosis. The nuclei of the dead hepatocytes were stained positively by the TUNEL method. Lactate dehydrogenase (LDH) release, which is considered leakage from apoptotic hepatocytes into the medium, was apparent at 24 h after DON addition. Increased caspase-3 activity was seen in DON 100, 10 and 1 microg/ml groups. Albumin secretion into the medium was significantly reduced in DON 100, 10 and 1microg/ml groups, moderately in the 0.1 microg/ml group, and slightly in the 0.01 microg/ml group. These results indicate that DON induced apoptosis through the caspase-3 activation pathway and caused functional disorder in porcine hepatocytes.