This chapter examines knowledge building (KB), which has been considered one of the exemplary dialogic approaches in computer-supported collaborative learning (CSCL) research. It aims to situate KB with other dialogic approaches, examining how progressive dialogue can be conceptualized, assessed and developed in technology-supported classrooms. The chapter discusses the centrality and nature of progressive dialogue in the knowledge age using the theoretical lens of KB. It also discusses Knowledge Forum (KF) affordances for supporting progressive dialogue. KB examines how people work together to advance the state of community knowledge; the goal of progressive KB dialogue is to generate and improve existing community knowledge. To support progressive dialogue, Scardamalia and Bereiter developed the Computer-Supported Intentional Learning Environment, one of the first CSCL platforms, in the late 1980s, followed by KF in 1997. While the notion of “collective” has been emphasized in dialogic and CSCL research, the KB model focuses more explicitly on collective progress as in knowledge creation in scientific dialogue.