This brief discusses some of the results and conclusions from the Professional Development Project of the National Institute for Science Education (NISE). The project was intended to explore whether the science, mathematics, and professional development communities share a common understanding of what professional learning experiences look like and how teacher development should be nurtured. A variety of standards and related materials were reviewed as part of the project, and a listing of those is included. Seven principles that are found in excellent professional development experiences for science and mathematics educators are presented. The principles include ideas related to a clear, well-defined image of effective classroom learning and teaching; providing teachers with opportunities to develop knowledge and skills and broaden their teaching approaches; using instructional methods to promote learning for adults which mirror the methods used with students; building or strengthening the learning community of science and mathematics teachers; preparing and supporting teachers to serve in leadership roles; providing links to other parts of the educational system; and making continuous assessment part of the professional development process. (DDR)