The many aspects of audiovisual (AV) speech processing have attracted a loyal following from a wide range of perspectives and disciplines. Beginning with the landmark NATO workshop in 1995 [50], a series of international special sessions and meetings has fostered the development of numerous lines of AV speech research. This paper is an introduction to the special session and an inventory of several developments in the area. The introduction is organized around three questions concerning human and machine performance-when, where, and how AV speech processing occurs-and a summary of applications, including AV speech recognition and synthesis, AV processing with cochlear implants, and AV effects observed in second language learners.