In order to increase the quality and quantity of science instruction, elementary teachers must receive professional development in science learning processes. The current study was part of a larger randomized field study of teacher and student learning in science. In two districts in a southern state, researchers randomly assigned teacher participants to the experimental and control conditions. The current study reported the effects of 2 years of sustained, embedded professional development on Grade 2 through Grade 5 elementary teachers' science-process skills, as defined by their ability to design experiments, and teacher perceptions of their capacity to lead students in scientific explorations. The results revealed a statistically significant difference between the adjusted post-test scores for the two groups, with the experimental group scoring higher than did the control group, indicating a significant gain in teachers' science process skills. The results for teacher perceptions about their own science process skills revealed a statistically significant increase between pre- and post-test scores, with a large effect size reflecting a gain in teacher views of more than 2 points on a 4-point scale. The results for teacher perceptions about students' science process skills also revealed a statistically significant increase between pre- and post-test scores with a large effect size. The results of this study document the effects of sustained and targeted teacher professional development focused on improving content-specific science instruction for students in the elementary classroom. (Contains 2 tables.)