The paper is concerned with the image of relations between husband and wife presented in the thirteenth-century educational treatise De regimine principum by Giles of Rome. It belonged to the most popular ‘mirrors of princes’ in the Middle Ages. Giles shows how conjugal relations should be arranged primarily by outlining the husband’s duties to, and his treatment of, his wife. He is responsible for her moral development.He is to lead her to temperance, silence and stability (ad temperantiam & ad taciturnitatem & ad stabilitatem). In marital sex he is to comply with the Church’s teachings, to provide his wife with adequate material goods, to show signs of love, and to give appropriate warnings when her behaviour is improper. The instruction of how to deal properly with the wife is formulated by Giles in the context of the authority assigned toher husband over her, and consequently of his responsibility for guiding her. This prerogative of the husband is due to a woman’s natural subordination to a man because of his superiority over her in terms of prudence and reason. The government that the husband exercises over his wife should not be that of the parent over his child nor that of the master over his servant. He should treat his wife as a companion (tamquam socia).A natural element of conjugal relations is amicitia (love) that results – as it may be assumed – from living together, and that manifests itself in the ways spouses treat each other. The proper fulfilment of their duties by the husband and the wife was to guarantee their harmonious coexistence, although far more responsibility fell on the husband because of his natural superiority over the woman.