Primary care physicians often perceive patients as unlikely to decrease their substance use and suggest this reluctance to change diminishes their willingness to screen and intervene. The literature on readiness to change has primarily focused on adults, and the available studies on adolescents have largely included hospitalized and/or incarcerated youths with severe substance-related difficulties. The present study focuses on an urban primary care system's teenage population, which consists of youths typically engaging in less serious forms of substance use. One hundred sixty-eight of these youths ages 11 to 20 screened positive for substance use on a self-report questionnaire. These youths then completed the Readiness to Change Questionnaire. Nearly 60% of these positive screens were in the Action stage, with another 16% in the Contemplation stage. Depressive symptoms and suicidal ideation were positively associated with later stages of change. Implications for screening, prevention, and early intervention programs for adolescent substance use are discussed. (Contains 1 table.)