Dr. Horace Gerald Danner’s A Thesaurus of Medical Word Roots is a compendium of the most-used word roots of the medical and health-care professions. All word roots are listed alphabetically, along with the Greek or Latin words from which they derive, together with the roots’ original meanings. If the current meaning of an individual root differs from the original meaning, that is listed in a separate column. In the examples column, the words which contain the root are then listed, starting with their prefixes. For example, esthesia, which means “feeling,” has as its prefixed roots alloesthesia, anesthesia, and dysesthesia. The listing then switches to words where the root itself forms the beginning, such as esthesiogenesis or esthesioneuroblastoma. These root-starting terms then are followed by words where the root falls in the middle or the end, as in acanthesthesia, cryesthesia, or osmesthesia. In this manner, A Thesaurus of Medical Word Roots places the word in as many word families as there are elements in the word. This work will interest not only medical practitioners but linguists and philologists and anyone interested in the etymological aspects of medical terminology.