Mixtures is of central importance for Galen's views on the human body. It presents his influential typology of the human organism according to nine mixtures (or 'temperaments') of hot, cold, dry and wet. It also develops Galen's ideal of the 'well-tempered' person, whose perfect balance ensures excellent performance both physically and psychologically. Mixtures teaches the aspiring doctor how to assess the patient's mixture by training one's sense of touch and by a sophisticated use of diagnostic indicators. It presents a therapeutic regime based on the interaction between foods, drinks, drugs and the body's mixture. Mixtures is a work of natural philosophy as well as medicine. It acknowledges Aristotle's profound influence whilst engaging with Hippocratic ideas on health and nutrition, and with Stoic, Pneumatist and Peripatetic physics. It appears here in a new translation, with generous annotation, introduction and glossaries elucidating the argument and setting the work in its intellectual context.