This book constitutes the refereed proceedings of the 4th IEEE Tutorial and Research Workshop on Perception and Interactive Technologies for Speech-Based Systems, PIT 2008, held in Kloster Irsee, Germany, in June 2008. The 37 revised full papers presented together with 1 invited keynote lecture were carefully selected from numerous submissions for inclusion in the book. The papers are organized in topical sections on multimodal and spoken dialogue systems, classification of dialogue acts and sound, recognition of eye gaze, head poses, mimics and speech as well as combinations of modalities,...