The paper examines the conception of health of the Graeco-Roman medical and philosophical author Galen. On the basis of a range of texts, especially Matters of Health and Thrasybulus, the most significant and influential characteristics of this conception are considered: the twofold definition of health in terms of balance of elements and of organic function; the notion of a latitude within health; the extent to which health is conceived as a specialist expertise, and against this the possible role of the (...) patient in understanding his/her own health. Galen's health writings are also considered in their social-historical context and in relation to their intellectual predecessors – Hippocrates, Plato, Aristotle and a range.. (shrink)