Nonalcoholic steatohepatitis (NASH) refers to an alcoholic hepatitis-like histologic pattern found in nonalcoholic patients. A review of 543 liver biopsies diagnosed as alcoholic hepatitis yielded 49 cases of NASH. The patients were commonly middle-aged women who were obese and often diabetic. NASH was usually discovered because of abnormal liver function tests or hepatomegaly noted during evaluation of other medical problems. Histologic examination revealed the same spectrum of changes found in alcoholic hepatitis, including cirrhosis in eight patients. Follow-up information was available for 39 patients after an average length of 3.8 years. Only one patient developed hepatic decompensation or died with liver failure or portal hypertension. Repeat histologic material was available for 13 patients after a mean 3.5 years of follow-up. Five patients showed progression of fibrosis, with cirrhosis developing in two, but the other eight patients demonstrated little morphologic change. These findings indicate that NASH is, in general, a clinically mild and biologically low-grade condition, but with the potential to progress and evolve into cirrhosis in some patients. The factors promoting progression are unclear.