Opinions are frequently expressed in the medical literature whether patients should be addressed by their first or last names, but few supportive data are available. Our objective was to determine the preferences of a sample of ambulatory patients to guide physicians and other professionals in addressing their patients appropriately.Three hundred seventy-five patients in a variety of ambulatory settings were asked how they wished to be addressed by physicians in various contexts.When meeting a physician for the first time, 45 percent of the respondents wanted to be called by their first names, 29 percent preferred last names, and 26 percent found either approach acceptable. When being addressed by a physician with whom they were already well acquainted, 78 percent favored given names, and only 6 percent chose surnames. Preferences varied little with age of the patient or with age or sex of the physician.These data indicate that one cannot predict reliably how a new patient will prefer to be addressed but that the great majority of established patients will want to be called by their first names.