A software system designed to maintain protocol-specific investigational drug accountability records is described. The University of Texas M. D. Anderson Cancer Center and Cygnus Systems Development, Inc., worked together to create an electronic investigational drug accountability system (IDRx), which meets the requirements of the National Cancer Institute. This system performs record keeping, stores information on drugs and protocols, and generates standard and customized reports. On-screen assistance makes it easy to use. Security is achieved by granting access only to authorized users, and an audit trail is automatically generated. Systematic implementation at M. D. Anderson, initially in the investigational drug control area and subsequently in the satellite pharmacies, has resulted in increased accuracy and efficiency, and few problems have been encountered. The IDRx software package is useful for keeping records, generating reports, and tracking and evaluating data associated with an investigational drug accountability system.