A comprehensive, interdisciplinary approach for reducing the number of chemotherapy-related medication errors at the National Institutes of Health Clinical Center, where approximately 8500 doses of chemotherapy agents are dispensed annually, is described. Heightened awareness of the seriousness of chemotherapy-related medication errors prompted formation of an interdisciplinary task force in June 1995 to analyze and improve the hospital's system for ordering, checking, processing, and administering cancer chemotherapy agents. Problems were analyzed and rectified in accordance with the hospital's plan-do-check-act performance-improvement model. Performance monitors for the improvements included a system to record and categorize all chemotherapy-related prescribing errors and a hospital-wide occurrence-reporting system. The task force identified seven major categories in which improvements were needed: protocol development, computer-system enhancements, dose verification, information access, education for health care practitioners, error follow-up, and infusion pumps. Despite the Clinical Center's good safety-net system, 23 modifications were made to the existing system through December 1999. These changes resulted in an overall 23% decrease in prescribing errors and a 53% decrease in serious prescribing errors. The task force membership was recently broadened to include representatives of additional departments where chemotherapy agents are used, and this group recommended more than 20 additional system changes. The changes are being implemented, and their effect on reducing the number of chemotherapy-related errors will be measured. The continuous-improvement process used prospectively by the task force helps ensure that safe chemotherapy practices are instituted uniformly throughout the hospital.