This study examined the practice of two science teachers who increased the participation of minority students who historically had not participated or succeeded in science. The two teachers were identified through a process of recommendation, personal interview, and observation. Researchers captured the practice of both teachers throughout one semester using in-depth teacher interviews, participant observations, classroom documents, and interviews with students and colleagues. The principles of constructivist analysis guided the data analysis. A cross-case comparison revealed patterns of similarities and differences between the two teachers. For example, both emphasized a few key topics in their classes, respected students and their cultures, were professionally active in and out of school, had in-depth knowledge of science, and had high expectations for their students. Differences included the nature of their teaching and the nature of the classroom environment. The study suggests that teachers who are working with diverse populations should be sensitive to their students' backgrounds, hold high expectations for them, and develop an understanding of science that informs their practice. (Contains 26 references.) (SM)