▼ [ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Sexually transmitted infections (STIs) are a serious public health concern worldwide. In the United States, young adults are at particularly high risk for contracting STIs, due to increased engagement in casual sexual encounters and failure to consistently implement safe sexual practices. The goal of this study was to identify decision-making strategies in hypothetical sexual choice scenarios. A novel task was developed to identify how young adults make trade-offs between attractiveness and risk information and whether their choice preference behavior is most consistent with a compensatory or non-compensatory strategy. Furthermore, this study was designed to test associations between decision strategy use and personality traits, expectancies for sexual behavior, and past sexual behavior. The results of this study suggest that the vast majority of participants exhibited choice preference behaviors consistent with a compensatory strategy, indicating that they time-intensively weigh both attractiveness and STI risk information in hypothetical sexual situations. Follow-up analyses with p-median clustering techniques indicated between-participant variability, with individual differences in reliance on attractiveness versus risk information during decision-making. Further, cluster membership was meaningfully associated with STI severity, probability of STI contraction, and gender, but was not consistently associated with personality traits or engagement in risk-taking behaviors. Future directions include examining effects of acute alcohol intoxication on sexual choice preference behavior and expanding these mathematical modeling techniques to other types of risk-taking. Advisors/Committee Members: McCarthy, Denis (advisor).