In Taiwan, there has been an increase in biopsychosocial morbidity among adolescents in the past ten years, but neither an adolescent health care delivery system nor a subspecialty training program in adolescent medicine has been hitherto established. To better understand the characteristics of adolescent patients and their health problems, the sociodemography and health problems of all adolescent patients aged 11 to 21 years who visited the Adolescent Health Clinic twice or more during January, 1994 and December, 1995 at a college hospital, were analysed by reviewing patients' medical records and the adolescent registration records. There were totally 264 adolescent patients with an average age of 18.7 +/- 3.4 years. The number of female adolescents involved in the study (139 persons or 52.7%) was little more than that of male adolescents. Most of the adolescent patients (67.4%) were in late stage of adolescence; in addition, most of them (81.4%) were students. During the 2-year study period, there was a total of 350 independent health problems among 957 office visits made by the 264 patients, averaging 1.3 problems and 2.7 office visits per patient and per problem, respectively. Supplementary classification, mental disorders, and respiratory system diseases were the three leading disease classifications, occupying 66.6% of all disease classifications. General medical examination, upper respiratory tract infection, and immunization were more common among all individual diagnoses. Regarding gender difference in the encountered health problems, hepatitis B, office visiting for counseling, and conductive disorder, were more prominent in the male adolescents, whereas upper respiratory tract infection, goiter, acne vulgaris, peptic ulcer disease, migraine, and eating disorders were more common in the female adolescents. Moreover, the patients in the different stages of adolescence had their unique health problems. It was concluded that there were variations in the health problems encountered among adolescents of different genders and of the different stages of adolescence.