This study examined the perceptions and self-reported practices of 18 scientists participating in a yearlong seminar series designed to explore issues of gender and ethnicity in science. Scientists and seminar were part of the Promoting Women and Scientific Literacy project, a curriculum transformation and professional development initiative undertaken by science, science education, and women's studies faculty at their university. Researchers treated participating scientists as critical friends able to bring clarity to and raise questions about conceptions of inclusion in science education. Through questionnaires and semistructured interviews, we explored their (a) rationales for differential student success in undergraduate science education; (b) self-reports of ways they structure, teach, and assess courses to promote inclusion; and (c) views of androcentric and ethnocentric bias in science. Statistical analysis of questionnaires yielded few differences in scientists' views and reported practices by sex or across time. Qualitative analysis of interviews offered insight into how scientists can help address the problem of women and ethnic minorities in science education; constraints encountered in attempts to implement pedagogical and curricular innovations; and areas of consensus and debate across scientists and science studies scholars' descriptions of science. From our findings, we provided recommendations for other professional developers working with scientists to promote excellence and equity in undergraduate science education. © 2001 John Wiley & Sons, Inc. Sci Ed86:42–78, 2001.