First published in 1986. The important implications of speech variability for the future of speech related technology, in combination with the multifaceted debate about invariance among speech scientists, make this a most appropriate time to evaluate the state our knowledge in this area. On October 8-10, 1983 researchers from the fields of production, perception, acoustics, pathology, psychology, linguistics, language acquisition, synthesis and recognition met at a. symposium at M.I.T. on invariance and variability of speech processes. This volume is the Proceedings of the symposium. Each chapter of the book consists of a focus paper followed by some comments.