The objective was to assess the potential benefits of the routine use of the MOS SF-36 Health Survey (SF-36) in the care of ambulatory patients. The design was a longitudinal, prospective, randomized, controlled study set in the outpatient neurology clinic at the New England Medical Center. There were 163 consecutive patients with epilepsy who had 210 follow-up visits with one of two epileptologists. The patients completed the SF-36 before the patient-physician encounter and the forms were optically scanned. The SF-36 results of the intervention group patients were given to the physicians before the encounter and withheld for control group patients. For intervention group patients, the physicians completed a questionnaire assessing the impact of the SF-36 on the process of care. After the visit, all patients completed a satisfaction questionnaire. The main outcome measures were the physicians' responses to standardized questions about the usefulness of the SF-36 for communication with and management of epilepsy patients and the patients' responses to standardized questions about their satisfaction with care. The physicians indicated that the SF-36 provided new information in 63% of the intervention group encounters. A change in therapy was prompted in 13%. The physicians rated the SF-36 as at least moderately useful for communication in 14% of the encounters and to management in 8%. The lower (indicating worse health status) the patients' SF-36 scale scores, the more useful the SF-36 results were rated by the physicians for communication and management. It was concluded that the routine use of health status measures may enhance patients' care.