In De tremore, rigore, palpitatione, et convulsione liber, a forgotten work preserved in ten Greek manuscripts and in some medieval translations into Latin, Galen described four types of abnormal involuntary movements: tremor, rigor, palpitation, and spasm. De tremore provides the first detailed description of these movement disorders in the western medical tradition and it became one of the most quoted and influential texts in the history of neurology and neuropathology (e.g., Parkinson and MS). Galen’s questions about the nature of these neurological conditions are still relevant today and some of them have not been resolved yet. Furthermore, De tremore represents an authoritative source for understanding some key concepts of ancient neurophysiology and the legacy of humoral theory in the history of western medicine (e.g., motor impulse, innate heat, psychic pneuma, voluntary motions, etc.). This volume offers a new complete critical edition of the Galenic text, with an introduction, English translation, commentary, reception history and indices.