Medical informatics deals with all aspects of understanding and promoting the effective organization, analysis, management, and use of information in health care. This report describes a select few of the computer systems that the Agency for Healthcare Research and Quality (AHRQ) has supported. These systems are relevant to the problems clinicians face, such as improving the quality of patient care and patient safety, preventing medical errors, reducing costs, helping patients manage their conditions, and minimizing the impact of bioterrorism.