The objectives of the study were (a) to determine psychosocial determinants of two measures of health care use: seeking a second opinion and alternative medicine use, and (b) to assess whether changes in these two measures of health care use had taken place during the past 4 to 5 years. All patients attending a university-based gastroenterology clinic were asked to complete a self-administered questionnaire. The response rate was 83% (N = 341). Health locus of control, scepticism toward medicine, satisfaction with health care, and perceived health status were included as potential determinants. Sixteen percent (21) of the new patients (95% confidence interval, 10.0-22.8) sought a second opinion compared to 7.5% (95% confidence interval, 4.3-10.7) 5 years ago. Seeking a second opinion was negatively related to internal locus of control, perceived health status, and demanding to know all details of treatment. Eight percent (28) of all patients (95% confidence interval, 5.3-11.1) saw an alternative practitioner for the same problem for which they saw the gastroenterologist compared to 9% (95% confidence interval, 6.2-12.8) 4 years ago. Using alternative medical care was positively related to scepticism toward conventional medicine and negatively related to perceived health status and satisfaction with clinic physicians. Knowledge about the incidence and determinants of these behaviors provides valuable information for clinicians in communicating with their patients and may eventually result in cost containment.