This is the first modern English translation of Dioscorides’ monumental De materia medica, written in the first century of our era. It is based on the Greek text established by Max Wellmann in 1906–1914. The medicinal materials of which the sources, preparations, and uses are described include more than 600 plants, 136 animals and animal products, and over 130 minerals. The identification of plants is based on the most recent scholarship on ancient Graeco-Roman botany. In the third edition, as in the second, the author had added three indexes: Index of Plants and Plant Products: Greek-English, Index of Animals and Animal Products: Greek-English, Index of Minerals and Mineral Products: Greek-English that together with the original indexes now offer easy access to the text from either language. Following the suggestions of readers and reviewers, this fourth edition has an additional index: Index of Plants: Botanical Names-Greek-English. The book will be of interest to classical philologists, to historians of medicine and of science, to ethnobotanists and other anthropologists, and to research pharmacologists who explore ancient and folk medical practices in the search of new chemotherapies.