Youths who are incarcerated often have high risk behaviors for HIV. A descriptive qualitative approach was used to gain an understanding about perceptions of HIV risk-taking behaviors among male youths who were incarcerated in a juvenile vocational training center in the north of Thailand. Multiple methods were employed to gather information from 42 male youth and included site document reviews, four focus group discussions (8 persons/group), 10 in-depth interviews, and participant observation. Data were analyzed using qualitative content analysis. Two themes emerged. The first theme was Personal perceptions of risky behavior and this had five subthemes: The nature of adolescents and risk behaviors, Stress in vocational training, Surviving the training, Needing the excitement of sex, and Sexual norms. The second theme, Social and environmental contexts encouraging HIV risk-taking behavior, involved three subthemes: Rules and regulations promoting risky behaviors, Incitement to risky behaviors, and Peer influence. Accurate understanding about HIV risk-taking behaviors of youths who are incarcerated will help nurses and other healthcare providers to provide sensitive health care to these youths and to mutually engage to support those incarcerated to reduce HIV risk-taking behaviors.