Pharmaceuticals used to treat hematologic malignancies can lead to unexpected adverse events that involve a wide range of organ systems and physiological processes. The National Cancer Institute and National Heart Lung and Blood Institute-funded Research on Adverse Drug Events and Reports (RADAR) project-a collaboration of the Robert H. Lurie Comprehensive Cancer Center, the Department of Veterans Affairs, the Northwestern University Feinberg School of Medicine, and numerous academic institutions-identifies and evaluates unexpected adverse drug reactions associated with drugs used to treat malignant disorders. This article reviews the features of the safety program maintained by the U.S. Food and Drug Administration and the RADAR program.