Knowledge mapping is expected to measure deep conceptual understanding and allow students to characterize relationships among concepts in a domain visually. This research examined the validity of knowledge mapping as an assessment tool in science. The approach to investigating this validity was three-pronged. First, a model was outlined for the creation of knowledge mapping tasks, proposing a standard set of steps and using content area and educational experts to ensure the content validity of the measures. Next, a scoring method was developed to evaluate student performance. This report contains a discussion of the methods reliability and its relation to other possible scoring systems. Finally, the report presents the statistical results based on the participation of 56 fourth and fifth graders, including comparative analyses, the multitrait-multimethod (MTMM) validity analyses involving two traits (students understanding of hearing and of vision), and three different measurement methods (knowledge mapping, essay, and multiple-choice tasks), critical proposition analyses, and analyses of students, propositional elaborations. Results show knowledge maps to be sensitive to students competency level, with mixed MTMM results. The report concludes with a discussion of implications and directions for future work. (Contains 7 tables, 2 figures, and 33 references.) (Author/SLD)