OBJECTIVES: To determine the prevalence, pattern, and out-of-pocket expenditure of complementary and alternative medicine (CAM) utilization in Korean adult population. METHODS: We conducted a representative telephone survey of 2,042 persons aged 18 or older. Data about any health problem, details of their use of medical doctors(MDs) offices/hospitals/ pharmacies services and CAM during the preceding 12 months were collected with structured questionnaire. RESULTS: The utilization rate of CAM among Korean adults was 29% in one year. A total of 231 kinds of CAM was identified from this survey. Annual out-of-pocket expenditure associated with CAM use in 1998 amounted to pound $1.88 billion and was comparable to 40.8% of out-of-pocket expenditure paid for MDs offices/ hospitals/pharmacies services. Among those(N=424) who paid for both MDs offices/hospitals/pharmacies services and CAM, 35.8% paid more for CAM. CAM gave more satisfaction than western medicine to those who had experience of both types of therapy. About half of CAM users were willing to recommend CAM to others. Disclosure rate to physician among CAM users was not high(40.6%). CONCLUSION: CAM became a popular source of health care in Korea. Korean spent a substantial amount of out-of-pocket money on CAM without any public control. Because CAM use is likely to be increased rapidly through lay referral system, health policy makers and health professionals should pay more attention to CAM for making appropriate utilization of CAM.