Because pedagogical content knowledge (PCK) includes teachers' understanding of how students learn, or fail to learn, specific subject matter, the development of PCK is an important goal to focus on in professional development programs. The research literature clearly indicates the complex nature of PCK as a form of teachers' professional knowledge that is highly topic, person, and situation specific. This implies that professional development programs aimed at the development of teachers' PCK cannot be limited to supplying teachers with input, such as examples of expert teaching of subject matter. Instead, such programs should be closely aligned to teachers' professional practice and, in addition to providing teachers with specific input, should include opportunities to enact certain instructional strategies and to reflect, individually and collectively, on their experiences.