Achieving scientific literacy is an essential outcome of science education and is comprised of knowledge of scientific content, the process of scientific inquiry, and understanding the Nature of Science (NOS; National Research Council, 1996). NOS refers to the characteristics of scientific knowledge that are derived from the results of the process of inquiry, or the epistemology of science. This study investigates the change or retention in Nature of Science (NOS) understandings held by participants (n=61) at the ages of 8 and 18. Results of previous research typically suggest that students and teachers of science alike hold inadequate NOS understandings. However, how might NOS understandings change, particularly for those that do understand some dimensions? Interview responses at two time-points on similar instruments were qualitatively and then quantitatively analyzed. Results of quantitative analysis suggest that there were changes in responses to three out of the four dimensions assessed. Understandings of dimensions including the subjective NOS and tentative yet reliable NOS improved over time. Understandings of the difference between inference and direct observations changed, but evidence suggests that they did not improve; participants' understandings were adequate for their age during the earlier assessment but failed to become more complex as they progressed through their education. Lastly, many participants retained naive understandings of the empirical NOS. Overall, approximately 25% of participants in this study improved their understanding on three or all four NOS dimensions assessed. Additionally, no gender differences were found, mirroring some findings in NOS literature (Moss et al., 2001). To further investigate potential sources of support for adequate NOS understandings, further qualitative analysis of interviews from participants and their parents explore a possible connection between interest in science and parent education level. These connections warrant further research. These findings are compared to evidence from past NOS research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]