Abstract: The purpose of this study was to examine (a) college students' attitudes and complexity of thinking about the Endangered Species Act (ESA) and (b) the effects of environment-based coursework on students' attitudes and thinking. Using self-report questionnaires in a pretest-posttest design, the authors examined attitudes in terms of their direction, extremity, ambivalence, and importance. Complexity of thinking was measured as integrative complexity. Results suggested that college students (N = 205) who had moderate and ambivalent attitudes toward the ESA wrote significantly more integratively complex essays about the issue than did students who had unambivalent attitudes. Students' integratively complex thinking was not related to the direction of their attitudes toward the ESA or its personal importance to them. Students who were enrolled in an environment-based, university-wide writing course showed a significantly greater increase in integratively complex thinking about the ESA than did students enrolled in a nonenvironment-based, university-wide writing course.