The purpose of this study is to establish retrospectively a nationwide registry of patients who have suffered drug-induced liver injury (DILI), and to collect, immortalize and store serum, DNA, and lymphocytes from these patients. ILIAD will serve as a resource for subsequent mechanistic investigations into the basis of severe idiosyncratic DILI. The primary goal of the ILIAD protocol is to create: (a) a clinical database consisting of individuals who have experienced severe DILI caused by four specific drugs, and the relevant clinical data concerning the episode of DILI; and, (b) to create a bank of biological specimens obtained from these individuals. These biological specimens will be DNA, plasma, and immortalized lymphocytes. Immortalized lymphocytes will provide unlimited amounts of genomic DNA for study as well as living immune cells for phenotyping studies. A secondary goal of the ILIAD protocol is to maintain a registry of cases in the ILIAD database so that they may be recontacted in the future. It is expected that this will facilitate additional studies exploring the mechanisms of DILI.