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 non-science majors—responded to the Science Motivation Questionnaire II, which assessed five motivation components: 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 non-science majors on all of the motivation components. 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