For the past five years, teachers from four Houston-area school districts have joined together in a professional learning community (PLC) to improve their science teaching. Through the University of Houston-Clear Lake (UHCL) Regional Collaborative for Excellence in Science and Mathematics Teaching, the teachers strengthen content knowledge and share teaching strategies that they then bring back to their home schools as science teacher mentors. Results for the teachers include increased knowledge on science topics (as measured in pre- and posttests), as well as gains in self-confidence, motivation, and leadership skills. Results for students include involvement in more hands-on and lab-based science to prepare them for middle and high school, as well as improved Texas Assessment of Knowledge and Skills (TAKS) science scores. In this article, the authors describe how the collaborative works, including its use of the environmental education program Project Learning Tree (PLT) as a thread that connects the collaborative members. They also suggest ideas for teachers who are interested in creating or joining a professional learning community. (Contains 3 online resources.)