Adolescents are a high risk group for HIV infection and the characteristics of their partners may affect their susceptibility to infection. The goal of this study was to examine the effects of partner characteristics on sexually transmitted disease (STD) infection in a national sample of adolescents. Data from 8,024 sexually active adolescents who participated in the National Longitudinal Study of Adolescent Health (Add Health) in the United States were included in this study. Logistic models were used to examine the association of partner characteristics including age, neighbourhood, ethnicity, and school attendance on the self-report history of STD infection. The partner characteristics of age and school attendance were associated with the reporting of STD infection. The odds ratio for STD infection was 1.46 (95% confidence interval (CI) (1.22-1.75), P < 0.01) if the adolescent's partner was two or more years older and 1.37 (95% CI (1.16-1.62), P < 0.01) if the partner did not attend the adolescent's school. The odds ratios for having an older partner were also significant and positive for eight different STDs. Partner characteristics were associated with STD infection among American adolescents. Counselling is needed in clinics that serve adolescents to raise awareness of the risk of infection in these relationships and to improve skills in condom negotiation and use.