We designed this observational cohort study to assess the association between patient-centered communication in primary care visits and subsequent health and medical care utilization. We selected 39 family physicians at random, and 315 of their patients participated. Office visits were audiotaped and scored for patient-centered communication. In addition, patients were asked for their perceptions of the patient-centeredness of the visit. The outcomes were: (1) patients' health, assessed by a visual analogue scale on symptom discomfort and concern; (2) self-report of health, using the Medical Outcomes Study Short Form-36; and (3) medical care utilization variables of diagnostic tests, referrals, and visits to the family physician, assessed by chart review. The 2 measures of patient-centeredness were correlated with the outcomes of visits, adjusting for the clustering of patients by physician and controlling for confounding variables. Patient-centered communication was correlated with the patients' perceptions of finding common ground. In addition, positive perceptions (both the total score and the subscore on finding common ground) were associated with better recovery from their discomfort and concern, better emotional health 2 months later, and fewer diagnostic tests and referrals. Patient-centered communication influences patients' health through perceptions that their visit was patient centered, and especially through perceptions that common ground was achieved with the physician. Patient-centered practice improved health status and increased the efficiency of care by reducing diagnostic tests and referrals.