This study reports on the analysis of audiotapes of 537 adult, chronic disease patients and their 127 physicians (101 men and 26 women) in a variety of primary care practice settings to explore differences attributable to the effects of the patient's and the physician's sex on the process of communication during medical visits. Compared to male physicians, women conducted longer medical visits (22.9 vs 20.3 minutes; F(1,515) = 7.9, P less than .005), with substantially more talk F(1,518) = 19.5, P less than .000. Differences were especially evident during the history segment of the visit when female physicians talked 40% more than male physicians (F(1,518) = 20.1, P less than .000) and when patients of female physicians talked 58% more than male physicians' patients (F(1,448) = 24.4, P less than .000). Compared to male physicians, female physicians engaged in more positive talk, partnership-building, question-asking, and information-giving. Similarly, when with female compared to male physicians, patients engaged in more positive talk, more partnership-building, question-asking, and information-giving related to both biomedical and psychosocial topics.