Most studies on mental health in the adult population have found a significant relationship between mental health and social class. No study has thoroughly examined this relationship in the adolescent population. This article, based on the Bachman, O'Malley, and Johnston “Youth in Transition” data set, tests the social class/mental state relationship among adolescents. Three separate measures—well-being, psychiatric symptoms, and depression—are used to indicate mental state. Social class is based on a composite measure of socioeconomic level that exists within the “Youth in Transition” data set. Surprisingly, no relationship was found. These results persisted even when more traditional measures of social class based on parents’ education and the Duncan ranking of the fathers’ occupations were substituted for socioeconomic level. An alternative explanation supporting social stress is discussed in light of Thornberry's developmental hypothesis. © 1990 Taylor & Francis Group, LLC.