This article describes a quasi-experimental evaluation of a community-based, culturally and ecologically tailored HIV prevention intervention for Mexican American female adolescents grounded in the AIDS risk reduction model. A total of 378 Mexican American female adolescents (mean age = 15.2) participated in either the nine-session SHERO's (a female-gendered version of the word hero) intervention or a single session information-only HIV prevention intervention. Assessment data were collected at pretest, posttest, and 2-month follow up. Significant improvements across all time points were revealed on measures of self-esteem, condom attitudes, beliefs regarding a woman's control of her sexuality, beliefs regarding sexual assault, perceived peer norms, and HIV/AIDS and STI knowledge. At posttest SHERO's participants were more likely to carry condoms and to report abstaining from vaginal sex in the previous 2 months; and at 2-month follow up they reported using condoms more often in the preceding 2 months and planned on using them more frequently in the coming 2 months. Findings support the development of community-based adolescent HIV prevention interventions that address culturally specific ecological factors.Sexually transmitted infections (STIs), including HIV, continue to threaten the health of Latinas in the United States. Rates for chlamydia were three times higher and rates for primary and secondary syphilis were nearly two times higher among Latina females than Whites (Centers for Disease Control and Prevention [CDC], 2007). In 2006, Latinas made up 11% of the U.S. female population but accounted for 15% of females living with HIV/