The purpose of this study was to assess the impact of AIDS-related knowledge and attitudes of prostitutes on condom use from diverse 'sex markers' in Korea. The data were collected by interviewers at five different 'sex markets'. During March 1993, research assistants at the Institute of Health Services Research interviewed 371 prostitutes visiting sexually transmitted disease (STD) clinics. Multiple regression method was used in identifying the determinants of condom use. The level of condom use was regressed on personal characteristics of prostitutes, AIDS-related perceptions, and market type. Prostitutes' level of condom use turned out to be different across the markets featuring diverse types of services and fees. Neither perceived vulnerability nor perceived seriousness of AIDS had significant effects on condom use. Our findings suggested that the many AIDS-preventive educational efforts by STD clinics are ineffective. Hence, individual STD clinics need to develop AIDS-preventive education programs which are suitable for the unique circumstances of their respective 'sex markets'.