Abstract: From the perspective of social cognitive theory, the motivation of students to learnscience in college courses was examined. The students—367 science majors and 313 nonsciencemajors—responded to the Science Motivation Questionnaire II, which assessed five motivation compo-nents: intrinsic motivation, self-determination, self-efficacy, career motivation, and grade motivation.Exploratory and confirmatory factor analyses provided evidence of questionnaire construct validity.The motivation components, especially self-efficacy, were related to the students’ college science gradepoint averages. The science majors scored higher than the nonscience majors on all of the motivationcomponents. Among both science majors and nonscience majors, men had higher self-efficacy thanwomen, and women had higher self-determination than men. The findings suggest that the questionnaireis a valid and efficient tool for assessing components of students’ motivation to learn science in collegecourses, and that the components play a role in students’ science achievement. ß 2011 WileyPeriodicals, Inc. J Res Sci Teach 48: 1159–1176, 2011Keywords: motivation; assessment; validation; college science