To identify risk behaviors and psychosocial characteristics associated with high school students' selling drugs. In 2000, an anonymous standardized survey assessed substance use, drug selling and related risk factors (e.g., friends' use; messages about use) among high school students (n = 38,999) in a large metropolitan area. The sample was 51% female and included adolescents who were white (70%), African-American (18%), Asian (3.3%), Hispanic (1.7%) or who reported other ethnicities (7%). Logistic regression analyses examined whether selling drugs was associated with variables from different explanatory models, net of risk behavior and demographic characteristics. Twelve percent of students reported selling drugs in the past year. In the final logistic regression model, selling drugs was associated with being male, violence, delinquency and marijuana use. Students who sold drugs were less involved in religious and family activities but did not differ in their perceptions of, or participation in, school. Friends and school adults' support of substance use was associated with selling drugs, as was daily employment. Social competence, but neither purposeful planning nor self-efficacy, was associated with selling drugs. Despite popular perceptions, drug selling is not limited to out-of-school youth but occurs frequently among students who attend high school. School-based prevention efforts should discourage drug selling in order to reduce students' access to drugs and protect young people from the dangers associated with drug selling.