The use of concept maps as instruments for assessing preservice teachers’ epistemologies of science (their ideas of the nature of scientific knowledge) was evaluated in this study. Twenty-three preservice elementary teachers’ responses to the Views of the Nature Of Science (VNOS) questionnaire were compared to concept maps created in response to the general probe, “What is science?” While VNOS responses allowed a richer analysis of the content and quality of the participants’ epistemologies, the concept maps provided information about structural changes of participants’ epistemologies as well as how those epistemologies relate to their overall conceptions of science as a field of study. Both instruments also revealed important connections between NOS tenets, which were more numerous on the concept maps but more informative on the VNOS, and between NOS tenets and pedagogical issues. Implications for assessment of students’ epistemologies of science in classrooms are discussed.