This article uses an existing evaluation framework to exemplify how an organic chemistry program for high school teachers facilitated their professional development. Chemistry teachers from 6 different high schools participated in the program. The professional development program was informed by a constructivist theoretical background in which teachers' situated learning and sociocultural factors were central to supporting meaningful learning. To facilitate teachers' professional development, the researcher worked, recurrently, with 6 high school chemistry teachers over 3.5 years. This article identifies the key elements of the professional development program that influenced change in the teachers' practices. Analysis of qualitative data collected showed that the hybridisation of the professional learning and teaching space, the nonhierarchical role of the program facilitator, and a focus on student learning were characteristic factors that contributed to the change in teachers' practices. The salient implications for teacher professional development and teacher learning are discussed.