Context .- Drug-induced liver injury (DILI) represents a diverse set of responses following exposure to any manufactured or naturally occurring chemical compound. Drug-induced liver injury is of major concern owing to the ever increasing number of compounds introduced into the market for treatment of various diseases as well as the increasing popularity of herbals, which lend themselves to self-medication but are not rigorously regulated. Objective .- To provide an overview of the prevalence, classification, and diagnosis of DILI with emphasis on pathogenesis and the role of a liver biopsy. To focus on the most common, emerging, and herbal agents that cause DILI with emphasis on the histologic pattern of injury observed. Data Sources .- A review of the literature was drawn from the PubMed (US National Library of Medicine) repository, textbooks, and online databases. All figures were taken from cases seen at our tertiary referral center, which is 1 of 12 participating sites in the National Institutes of Health-funded Drug-Induced Liver Injury Network. Conclusions .- Drug-induced liver injury due to prescription, over-the-counter, and herbal products is a major cause of liver disease in the United States and around the world. Diagnosis of DILI is challenging because there is no single clinical, laboratory, or histologic feature specific to DILI. Accurate diagnosis requires establishing a causal relationship with the suspected agent and excluding competing causes of liver injury. The liver biopsy is an essential component in the management of DILI by offering clues to the underlying pathogenesis, providing prognostic information, and guiding therapy.