This study examined the impact of a professional development intervention aimed at helping elementary teachers incorporate elements of students' home language and culture into science instruction. The intervention consisted of instructional units and materials and teacher workshops. The research involved 43 third- and fourth-grade teachers at six elementary schools in a large urban school district. These teachers participated in the intervention for 2 consecutive years. The study was conducted using both quantitative and qualitative methods based on focus group interviews, a questionnaire, and classroom observations. The results indicate that as teachers began their participation in the intervention, they rarely incorporated students' home language or culture into science instruction. During the 2-year period of the intervention, teachers' beliefs and practices remained relatively stable and did not show significant change. Possible explanations for the limited effectiveness of the intervention are addressed, and implications for professional development efforts are discussed. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 44: 1269–1291, 2007