This article presents an overview of interest research and describes the theoretical and methodological background for the assessment of interest in science in large-scale assessments like the “Programme for International Student Assessment” (PISA). The paper starts with a short retrospective on the history of interest, bringing out theoretical roots that help to understand recent discussions on interest in science education. As interest is a widely used concept with manifold facets, it is essential to discuss different ways of modelling the relationship between a person and a comprehensive object like Science with all of its different aspects, including wide ranges of content as well as contexts. Models that can be used for describing the content structure of science interest and the process of interest development are presented. Based on an overview of typical methods for assessing interests, exemplary findings on students’ interest in science are presented which play an important role in the current scientific debate. Finally, challenges for future research on interest in science education are discussed.