Active principal leadership can help sustain and scale science curriculum reform. This study illustrates how principal leadership developed in a professional learning community to support a technology-enhanced science curriculum reform funded by the National Science Foundation. Seven middle school and high school principals in one urban-fringe district participated in the community for 3 years. Principals' ideas about leadership in technology-enhanced science grew in complexity over time. Initially, principals focused on learning specific features of the new science curriculum. Over time, they began sharing problem-solving approaches for integrating technology-enhanced inquiry curriculum into the school and district. Principals shifted from gathering information from outside experts to leveraging the knowledge within the group. Each principal in the community customized the codeveloped leadership and carried it back to his or her school site. This study suggests strategies for structuring environments to foster leadership for science instructional improvement. (Contains 5 tables and 2 figures.)