This study examined the psychometric properties of a new scale to measure adolescents' worry regarding outcomes of risky sexual behavior (i.e. sexually transmitted infections, including HIV [STI/HIV], and unintended pregnancy). The 10-item worry about sexual outcomes (WASO) scale, resulting in two subscales STI/HIV worry and pregnancy worry, was administered to a sample of 522 African-American female adolescents ranging in age from 14 to 18, residing in the southeast United States and participating in a sexual risk reduction intervention. The WASO demonstrated internal consistency across multiple administrations and yielded satisfactory construct validity. Worry was found to negatively correlate with sexual communication self-efficacy (with a new male partner and a steady male partner), frequency of sexual communication with male partner, attitudes about condom use and social support; worry was positively correlated with perceived barriers to condom use, condom negotiation, locus of control and depression. Overall, the results indicate that the WASO is a reliable and valid measure of assessing adolescents' worry about STIs, HIV and pregnancy. The WASO represents a brief self-administered instrument that can be easily integrated into sexual risk reduction assessments and interventions. Future studies employing the WASO might consider testing it with more diverse samples in terms of gender, race/ethnicity, age and sexual orientation. (Contains 5 tables.)