Implementation of practice guidelines remains problematic in spite of enormous efforts to develop and disseminate them, to establish their credibility, and to create incentives for physicians to adopt them. These strategies have failed to systematically change physician behavior because they do not address the involuntary time and mental processing constraints that have been clearly demonstrated to hamper physicians' ability to comply with guidelines. Computerized patient record systems directly address these constraints, and evidence is mounting that they are effective tools for changing physician behavior. A properly configured computerized patient record system provides decision support, facilitates work flow, and enables the routine collection of data for performance feedback. A synthesis of relevant research from the domains of practice guidelines and medical informatics strongly suggests that the operational support provided by computerized patient record systems will have a major impact on physician compliance with practice guidelines.