Objective To explore age differences in factors associated with positive sexually transmitted diseases (STD) status among a sample of African-American adolescent females. Methods Data were collected via ACASI from 701 African-American adolescent females (14–20 years) seeking services at reproductive health clinics. Adolescents provided self-collected vaginal swabs assayed using NAAT to assess the prevalence of three STDs. Results Younger adolescents (14–17 years) had significantly higher rates of STDs than older adolescents (18–20 years), but older adolescents had significantly higher levels of STD-associated risk behavior. In controlled analysis, having a casual sex partner was the only variable significantly associated with a positive STD test for younger adolescents, and prior history of STD and higher impulsivity were significantly associated with testing STD positive among older adolescents. Conclusions These findings suggest that developmentally tailored STD/HIV prevention interventions are needed for younger and older subgroups of adolescent females to help reduce their risk of infection.