We report the cases of 2 female patients aged 69 and 61 yr, suffering from fulminant hepatitis induced by pirprofen, a new nonsteroidal antiinflammatory drug. The duration of pirprofen administration before the onset of hepatitis was long, 7 and 9 mo, respectively. Hepatitis was not preceded or accompanied by hypersensitivity manifestations. The liver lesion consisted of massive, predominantly centrilobular hepatic cell necrosis and microvesicular steatosis. One patient died of liver failure. Although the risk of fulminant hepatitis is very low, we recommend that, in patients taking pirprofen for more than 2 mo and complaining of asthenia, nausea, or vomiting, serum aminotransferase levels should be measured and administration of the drug should be interrupted as soon as an increased level is noted.