The purpose of this paper was to investigate the related factors between two patterns of health service utilization: one, the single-method treatment (seeking help from either Western medicine or Chinese medicine only); the other, a dual-method treatment (seeking help from both Western medicine and Chinese medicine). Applying Andersen's health-service utilization model, an analysis was made by the basic demographic, enabling and need factors relating to differences between the two treatment patterns. During the period August to October, 1989, systematic sampling was done and a structured questionnaire survey was carried out among patients from the Outpatient Departments of 13 teaching hospitals which accept reimbursement by Labor Medical Insurance in Taiwan. The total number of valid respondents was 1128. Five hundred and seventy-nine patients received single-method treatment and 549 received dual-method treatment. Under univariate analysis, the significant variables (p＜0.05) related to the proneness to the single-method treatment were: males, people with college or higher education, unmarried people, people without medical insurance, people on their first visit, people seeking Western medical care, people considering themselves to he relatively healthy, or suffering from only minor illness, people suffering disorders of respiratory and other organs excluding neuro-musculoskeletal system. By logistic regression analysis, the significant variables related to the proneness to the dual-method treatment were visiting Chinese medicine clinics, having had bed rest during the past year, an illness with duration of longer than half a month, and the significant variables related to the proneness to the single-method treatment were visiting Western medicine clinics and illness with the first onset.