This fourth edition, like the first three, addresses the organic disorders of voice due to laryngeal structural changes and neurologic diseases, as well as the psychogenic voice disorders due to environmental stress and psychoneuroses and muscle tension dysphonias. This edition of Ginical Voice Disorders differs from previous editions by both the expansion and addition of chapters. The chapters are updated with current references and augmented with extended content. A DVD-R has been added with supplementary chapters, demonstration therapy, and interviewing. More specifically, organic evolution has been considerably expanded to include the photographs and concepts fleshed out by the late jan Wind, PhD, in his seminal work On the Ontogeny and the Phylogeny of the Human Lazynx(1970, Wolters-Noordhoff; out of print). Embryology of the larynx has been amplified, along with embryology of the respiratory system, and expanded to include many more detailed drawings illustrating the embryologic stages of both systems. Anatomy and physiology of voice production was revised by Susan L Thibeault, PhD, to include information on the microstructure of the vocal fold. Chapters on spasmodic dysphonias have been combined, updated, and revised. A new chapter, by Brian E. Petty, on the singer’s voice that addresses special issues related to the treatment of voice disorders in this population has been added. Psychogenic voice disorders now has extended case studies that relate personal stories behind this etiology of dysphonias and aphonias. The chapter on examination of voice disorders has been rewritten by Nathan V. Wellham, PhD. Greater descriptions of more voice therapy techniques and their underlying principles also have been included in this edition. In this work I reassert that the study of clinical voice disorders, and their diagnosis and treatment is now more than ever a medical subspecialty that requires highly specialized education and training of the speech language pathologist in order to interface with other members of the health care team.