The antineoplastic agents or anticancer drugs represent a large and diverse class of medications. They generally have limited but important uses, and often have significant hepatotoxicity.The antineoplastic agents are not easily classified. Historically, they are categorized as alkylating agents, antimetabolites, natural products, hormones and antagonists, and miscellaneous. In recent years, however, the miscellaneous group has come to include some of the most important agents. Anticancer agents can also be classified by indication (lymphoma, leukemia, melanoma, solid tumor), mechanism of action (such as alkylating agents, antibiotics, biological response modifiers, antiandrogens, topoisomerase inhibitors or protein kinase inhibitors), chemical structure (folic acid analog, platinum coordination complex, purine or pyrimidine analog, monoclonal antibody) or as cytotoxic or nonspecific vs noncytotoxic or targeted. The classification used in LiverTox represents a mixture of these systems, which generally follow those given in modern pharmacology textbooks.