This report describes two hospital-wide clinical computing systems that assist physicians, nurses, medical students, and other clinicians in the care of their patients. From any of the video-display terminals located throughout the hospitals (666 at Beth Israel Hospital and 1250 at Brigham and Women's Hospital, both in Boston), clinicians can obtain results from the clinical laboratories; read diagnostic reports from the clinical departments; view lists of medications used during hospitalization and prescriptions filled in the outpatient pharmacy; request delivery of a patient's chart; request consultation on approaches to therapy; perform bibliographic retrieval of the MEDLINE database; and read, write, retract, edit, and forward electronic mail. During a one-week study period, 1737 clinicians at Beth Israel Hospital used one or more of the options in the clinical information system 58,757 times. During the same week, 2262 clinicians at Brigham and Women's Hospital used one or more of their options 89,101 times. The large amount of use by clinicians, who could, if they so desired, rely on printed reports or telephone calls to obtain their clinical information, suggests that a reliable, comprehensive, and easy-to-use computer system can contribute substantially to the quality of patient care.