The work of Bishop and Anderson (1990) plays a major role in educators' understanding of evolution education. Their findings remind us that the majority of university students do not understand the process of evolution but that conceptual change instruction can be moderately effective in promoting the construction of a scientific understanding. The present article details two studies that represent an effort to focus on and define the limits of the Bishop and Anderson (1990) study. Study A describes a close replication of the work of Bishop and Anderson (1990) using the same conceptual-change teaching module to teach a unit on evolution to students enrolled in a biology course for nonmajors. Study B, a case of comparison, used the same evaluation instrument used in Bishop and Anderson (1990) and Study A, but high school students were the participants and the instruction was based on the inquiry approach to science. Like Bishop and Anderson (1990), Study A showed that the amount of prior instruction and students' beliefs in evolution were not found to be large factors in students' use of scientific conceptions. Unlike the original study, the students in Study A showed only a meager increase in their use of scientific conceptions for evolution. In Study B, students in the experimental group showed significant increases in their use of scientific conceptions. These findings suggest a need to investigate more closely the teachers' theories of learning, their reliance on instructional conversations, and the amount of time devoted to the topic of evolution as we study conceptual change in this area.