The clinical information available to clinicians is expanding rapidly. It can enhance clinical decision-making, but it can also confuse the process. To be most useful, information should be available at the time and place it is needed and be specific to the task at hand. In the new paradigm of medicine, one based on continuous quality improvement, useful information must be relevant to both the processes and outcomes of care. Clinical practice guidelines have become increasingly popular for improving the quality of health care. The field of medical informatics can bring cogent information to the point where decisions are being made to augment quality improvement activities in general, and practice guidelines in particular. However, such innovations are dependent on the type, quantity, and quality of information available. This article discusses when guidelines can enhance the quality and outcomes of care and how medical informatics can help achieve these goals. In particular, the barriers to the broad implementation of electronic medical records in a variety of health care settings are explored.