In view of the additional time that older persons require for giving and receiving information, as well as for the examination process, it is important for manpower and reimbursement planning to better understand the nature of the physician-patient encounter with the elderly. We examined a series of national surveys of physicians' professional activities and found that physicians tend to spend less time with their older patients and also that encounter time by physicians in different specialties varies widely. Internists and cardiologists spend substantially more time with patients compared with general and family practitioners. For 65-74-year-old ambulatory patients, the average visit lengths are 18.3 minutes for internists, 18.0 for cardiologists, 11.2 for general practitioners, and 12.1 for family practitioners. Compared with ambulatory visit lengths for patients aged 45 to 64 years, average encounter times for 75-year-olds with family physicians were 0.8 minutes shorter, with general practitioners 1.2 minutes shorter, with internists 2.3 minutes shorter, and with cardiologists 3.0 minutes shorter. However, when all characteristics of the visit were considered, the effect of patient age remained significant only for general practitioners. A multivariate analysis of factors related to physician time for ambulatory care showed that more time is associated with multiple problems, problem severity, and the use of diagnostic testing. For general and family practice, the greater the number of previous visits for a problem, the shorter the encounter time is. Additional characteristics associated with shorter physician-patient encounter times include the volume of patients per week and the use of physician assistants within the practice. These findings have implications for medical education and manpower projections.