This document discusses the Technological Pedagogical Content Knowledge (TPACK) framework for teacher knowledge. TPACK builds on Shulman's construct of pedagogical content knowledge to include technology knowledge. The TPACK framework argues that effective technology integration requires understanding the relationships between technology, pedagogy, and content. TPACK consists of seven knowledge areas and describes the complex interaction between content, pedagogy, and technology that produces flexible knowledge for technology integration in teaching. Measuring teacher TPACK is challenging and an area of ongoing research.