The Center for Learning Technologies in Urban Schools (LeTUS) is implementing a professional development program for science teachers to enact science curricula in a systemic reform initiative. This paper proposes a design approach for professional development in science education as a valuable way to re-conceptualize the process of fostering teacher learning. The paper presents an argument that professional development in science education, as a whole, has not been grounded in empirical research, and there is, therefore, a lack of sound design principles upon which to base professional development programs. One possible design model for professional development is posed in the context of the LeTUS systemic reform work, and evidence is given that illustrates the initial success of the model. (Contains 34 references.) (Author/WRM)