This study examines the development of technology, pedagogy, and content knowledge (TPACK) in four in-service secondary science teachers as they participated in a professional development program focusing on technology integration into K-12 classrooms to support science as inquiry teaching. In the program, probeware, mind-mapping tools (CMaps), and Internet applications--computer simulations, digital images, and movies--were introduced to the science teachers. A descriptive multicase study design was employed to track teachers' development over the yearlong program. Data included interviews, surveys, classroom observations, teachers' technology integration plans, and action research study reports. The program was found to have positive impacts to varying degrees on teachers' development of TPACK. Contextual factors and teachers' pedagogical reasoning affected teachers' ability to enact in their classrooms what they learned in the program. Suggestions for designing effective professional development programs to improve science teachers' TPACK are discussed. (Contains 1 table.)