This study assessed the representations of nature of science (NOS) in high school chemistry textbooks and the extent to which these representations have changed during the past four decades. Analyses focused on the empirical, tentative, inferential, creative, theory-driven, and social NOS, in addition to the myth of "The Scientific Method," the nature of scientific theories and laws, and the social and cultural embeddedness of science. A total of 14 textbooks, including five "series" spanning one to four decades, were analyzed. The textbooks commanded significant market shares in the United States and were widely used in some of the most populace states. Relevant textbook sections were scored on each of the target NOS aspects on a scale ranging from -3 to +3, which reflected the accuracy, completeness, and manner (explicit versus implicit) in which these aspects were addressed. The textbooks fared poorly in their representations of NOS. Additionally, with a few exceptions, textbook scores either did not change or decreased over the past four decades. These trends are incommensurate with the discourse in national and international science education reform documents, which has witnessed an increasing emphasis on the centrality of NOS to scientific literacy and pre-college science education during the same time period. Assessment and evaluation strategies, and policies need to be targeted if substantial and desired changes in the ways NOS is addressed in science textbooks are to be effected. (Contains 4 tables.)