Instituting reform in science education requires teachers who are knowledgeable in science content, process, and inquiry pedagogy. Most elementary and middle-grades teachers are not teaching reform-based science and need training to be able to do so. Project LIFE, a state systemic initiatives professional development program for middle-grades life science teachers, has been successful in improving the science content knowledge, process skills, and attitudes toward teaching science of 90 teachers during the first 3 years of the project. Data collected through classroom observations, surveys, and tests given to students of project teachers and students of matched nonproject teachers revealed a significant positive impact of the project in classrooms. The essential characteristics of the project are described as a guide for individuals planning or delivering reform-based science education professional development. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 73-88, 1998.