Two patients, both women aged 31 and 73 years, were admitted with chest pain and coma, respectively. They had very high aspartate aminotransferase levels, accompanied by relatively low alanine aminotransferase levels. The second patient had developed acute liver failure and hepatic encephalopathy. Both patients were chronic alcohol abusers and had taken therapeutic doses of acetaminophen for a couple of days. The marked elevation of the aminotransferase levels and the rapid decline of these levels after discontinuing the use of acetaminophen and alcohol led to the diagnosis of acetaminophen hepatotoxicity. In chronic alcohol abusers, cytochrome P450 2E1 is induced and the amount of glutathione is depleted. This combination causes the formation of a relatively large amount of the radical N-acetyl-p-benzoquinone imine and a low potential to detoxify this metabolite, so that even small amounts of acetaminophen may cause liver damage. It is recommended that chronic alcohol abusers (more than four alcoholic beverages per day) use no more than 2 g acetaminophen per day.