The present papers focus on Galen's (129–ca. 216) treatise On the elements according to Hippocrates, probably written ca. 169, during his second stay in Rome. According to Galen himself, the treatise was part of a wider ensemble dealing with the elements, along with two other treatises. Since the latter are mostly lost, the De elementis provides an invaluable testimony to Galen’s views on the elements, a question of the greatest importance in Ancient medicine. Despite not being a commentary as such on Hippocrates’ Nature of Man, although he later wrote one which does survive, Galen’s treatise features a defence of Hippocrates’ theses against his opponents. This issue collects 7 papers dealing with various aspects of Galen’s treatise, physical as well as linguistical or more philosophical, thus exemplifying the need to approach Galen’s work from multiple perspectives.