The United States Pharmacopeia (USP) Practitioners' Reporting Network utilized nearly three decades of experience to design and develop a nationwide, anonymous, Internet-accessible service for hospitals to report and benchmark medication errors (also known as "preventable adverse drug events"). As nationwide experiential reporting enters the 21st century, the features of MedMARx will provide facilities with the unprecedented ability to conduct daily continuous quality improvement that encompasses medication error risk analysis and prevention based on the experiences of other facilities. Data elements were developed based on review by expert panels and USP's experience with the Medication Errors Reporting Program. The success of this model could indicate its usefulness in other practice settings and for broader applications in health care.