Purpose: The purpose of this study was to identify factors to predict of condom use for the prevention of sexually transmitted diseases (STDs) among sex workers in a Korean community. The theoretical ground of this study was the Interaction Model of Client Health Behavior. Method: A descriptive, cross sectional and retrospective research design was employed in this study. A total of 100 sex workers who take a clinical check-up on STDs regularly at W Public Health Center were recruited by convenient sampling, and with consent to participate in this study. All of the measures were piloted, and the reliability of each scale ranged from 0.7 to 0.9. Data were analyzed using discriminating function analysis with SPSS-PC. Results: Five independent measures (partner preference for using condoms, subjects desire to prevent STD, age, type of relationship and sexual self-determination) contributed significantly to the best discriminating function. The discriminating function analysis resulted in correct classification of 83.1% of the respondents into their corresponding groups. Conclusion: Condoms are a main means of STDs prevention. Risk-reduction interventions that enhance communication skills and intrinsic motivation will be effective in increasing condom use to prevent STDs among sex workers.