Among 100 cases of hepatic injury attributed to the administration of pemoline, 43 had sufficient accompanying information to permit analysis. All but two patients were less than 20 years old, and 80% were less than 12 years old. Males predominated the study. Injury appeared as early as 1 week or as late as greater than 1 year of taking the drug. The injury was uniformly hepatocellular as judged by the high values for aminotransferases and by death in massive necrosis in one patient. Mechanism was judged to be idiosyncratic, and the idiosyncrasy was probably metabolic rather than immunologic.