Adverse drug reactions affecting the liver represent an important challenge for safety in drug development. Drugs can reproduce practically the whole spectrum of liver diseases, but acute hepatitis is the most common syndrome. Drug hepatotoxicity is one of the most common causes of fulminant hepatitis. Most hepatic drug reactions occur in only a small proportion of individuals, making them difficult to detect at the time of drug development. Liver injury is principally recognized on the basis of spontaneous reports within the first 2 years of marketing a new drug. The prevalence of drug hepatotoxicity is poorly documented by a small number of retrospective studies. Despite the development of international analytical methods to allow standardized evaluation, the diagnosis remains indeterminate in many cases. Acquired and genetic factors influence the individual susceptibility to drug hepatotoxicity. Important directions for the future include prospective studies of the incidence of hepatic adverse drug reactions, finding specific markers that augment or replace causality assessment, and further elucidating the role of the genetic and environmental factors that contribute to individual susceptibility.