The development of adequate student conceptions of the nature of science has been a perennial objective of science instruction regardless of the currently advocated pedagogical or curricular emphases. Consequently, it has been an area of prolific research characterized by several parallel, but distinct, lines of investigation. Although research related to students' and teachers' conceptions of the nature of science has been conducted for approximately 40 years, a comprehensive review of the empirical literature (both quantitative and qualitative) has yet to be presented. The overall purpose of this review is to help clarify what has been learned and to elucidate the basic assumptions and logic which have guided earlier research efforts. Ultimately, recommendations related to both methodology and the focus of future research are offered.