This study investigated the extent to which teacher professional development led to changes in science instruction in K-2 classrooms in rural school districts. The research specifically examined changes in (a) teachers' content knowledge in science; (b) teachers' self-efficacy related to teaching science; (c) classroom instructional time allotted to science; and (d) instructional strategies used in science. The study also investigated contextual factors contributing to or hindering changes in science instruction. Data sources included a teacher survey, a self-efficacy assessment, content knowledge tests, interviews, and classroom observations. After one year in the program, teachers showed increased content knowledge and self-efficacy in teaching science; they spent more instructional time on science and began using different instructional strategies. Key contextual factors included curricular demands, resources, administrative support, and support from other teachers.