This paper reports on sexual behavior, knowledge of sexually transmitted diseases (including AIDS) and condoms, and condom use among African-American and white incarcerated adolescents in Seattle, Washington. One hundred nineteen adolescents in a juvenile detention facility completed questionnaires that assessed their lifetime and recent sexual behaviors, an objective test of disease and condom knowledge, attitudes and norms regarding condom use with steady and casual partners, prior condom use, and intentions to use condoms. The results indicate that these adolescents are at high risk by a number of indicators: They have a high average number of partners, have unprotected vaginal and anal sex, and many have sex with known or suspected drug users. Their overall knowledge of condoms and sexual transmitted diseases risks is high, but high knowledge is not correlated with positive attitudes; for one attitude measure, high knowledge is significantly correlated with negative attitudes toward condom use. These findings suggest that programs designed solely to increase knowledge are unlikely to effect behavior change.