A wide range of drugs can induce thrombocytopenia. Molecular mechanisms for the formation of specific epitopes for all the drug-dependent antibodies appear to be very similar. A restricted set of glycoproteins on the platelet surface interacts with the drugs to form neoepitopes, to which the drug-dependent antibodies bind. Molecular mapping of antigenic sites may help characterize genetic polymorphisms that predispose to the formation of the antibody binding sites. Identification of antibody binding sites will enhance our understanding of the pathogenesis of immune drug-induced thrombocytopenia.