The search for new, authentic science assessments of what students know and can do is well under way. This has unearthed measures of students' hands-on performance in carrying out science investigations, and has been expanded to discover more or less direct measures of students' knowledge structures. One potential finding is concept mapping, the focus of this review. A concept map is a graph consisting of nodes representing concepts and labeled lines denoting the relation between a pair of nodes. A student's concept map is interpreted as representing important aspects of the organization of concepts in his or her memory (cognitive structure). In this article we characterize a concept map used as an assessment tool as: (a) a task that elicits evidence bearing on a student's knowledge structure in a domain, (b) a format for the student's response, and (c) a scoring system by which the student's concept map can be evaluated accurately and consistently. Based on this definition, multiple concept-mapping techniques were found from the myriad of task, response format, and scoring system variations identified in the literature. Moreover, little attention has been paid to the reliability and validity of these variations. The review led us to arrive at the following conclusions: (a) an integrative working cognitive theory is needed to begin to limit this variation in concept-mapping techniques for assessment purposes; (b) before concept maps are used for assessment and before map scores are reported to teachers, students, the public, and policy makers, research needs to provide reliability and validity information on the effect of different mapping techniques; and (c) research on students' facility in using concept maps, on training techniques, and on the effect on teaching is needed if concept map assessments are to be used in classrooms and in large-scale accountability systems. © 1996 John Wiley & Sons, Inc.