This book is intended in part to provide linguists and cognitive scientists who do not know sign language with a point of entry into the study of sign language phonology. At the same time, it presents a comprehensive theory of American Sign Language (ASL) phonology, while reviewing and building on alternative theories. The author is concerned to show both the similarities and differences between signed and spoken languages, and to indicate some directions for future work in cognitive science that can be derived from her phonological model.