The paper presents a model comprised of variables which are hypothesized to contribute to environmental knowledge in high school students. The model assumes that environmental knowledge in high school is a function of background factors (socioeconomic status and gender) which are in place before high school and intervening factors which mediate the effects of these background factors (locus of control, highest level of science class taken, and informal science activities). The sample consists of a national probability sample made up of approximately 2,900 high school students who are participating in the Longitudinal Study of American Youth. Bivariate analysis was used to examine the relationships between environmental knowledge and independent variables. Multiple regression procedures were used to analyze direct and indirect relationships among independent and dependent variables. Socioeconomic status, being male, and internal locus of control were all positively related to environmental knowledge. As expected, the level of science and amount of informal science exposure were also positively related to environmental knowledge. Implications for environmental education and recommendations for future models and research in this area are given. (LZ)