Instructional materials are an important resource in US classrooms. They represent the intersection of standards, subject matter knowledge and practice, and pedagogy. In light of the Framework for K-12 Science Education (National Research Council, 2012) and the subsequently released Next Generation Science Standards (Next Generation Science Standards [NGSS] Lead States, 2013), decision-makers need reliable information about the quality of instructional materials in science and the extent to which they embody the NGSS. This paper describes the development process and results of the "Guidelines for the Evaluation of Science Instructional Materials."