Purpose Receptive anal intercourse has long been recognized as a risk factor for the transmission of HIV and STIs. Most HIV/STI prevention messages continue to emphasize penile-vaginal transmission, so many teens do not recognize anal intercourse as risky sexual behavior. This purpose of this study was to determine the prevalence of anal intercourse, and to describe the relationship between types of sexual relationships (main vs. casual), types of sexual behaviors (vaginal vs. anal sex), and types of contraception used among inner-city sexually experienced adolescents. Methods Reproductive health histories were obtained from 350 sexually experienced adolescent females aged 12–18 years participating in a 5-year STI acquisition study at an urban health center. Baseline sexual behavior data was analyzed and described using frequencies, percentages and chi-square tests. Results 41% of teens and 86.5% of teens reported engaging in sexual activity with casual and main partners respectively. Sixteen percent of teens with main partners and 12% of those with casual partners engaged in receptive anal intercourse ( P = 0.31). Condom use is more prevalent for both vaginal (61% vs. 32.4%, P ≤ 0.0001) and anal (47.1% vs. 21.3%, P = 0.0428) intercourse in the context of casual as compared to main sexual relationships. Teens involved in a casual relationship were more likely to use anal intercourse as a form of contraception (41.2% vs. 8.5%, P = 0.0022). Conclusion It is imperative that health care providers recognize that adolescents engage in anal sex, specifically inquire about their types of sexual behavior and types of sexual relationships so that anticipatory guidance regarding HIV/STI transmission risk reduction education can be tailored to meet their needs.