Preventive medicine is taking an increasingly central place in modern clinical practice, at least in primary care. What, if anything, does the Jewish rabbinic tradition have to say about keeping healthy? The delayed response of contemporary rabbis to the dangers of smoking, in particular, raises questions about the underlying principles that Halakhah employs to approach health promotion. As is often the case in Halakhah, we may detect different streams of thought in the classical sources, which may be felt in the way contemporary issues are handled. Three approaches will be discussed. First, Maimonides, famous for the practical preventive approach in his medical writings, makes his philosophy clear both in his halakhic works and in his Guide for the Perplexed. For him, a healthy body is a prerequisite for a healthy soul. We must be free of physical suffering in order to be able to do the work of perfecting our souls. Second, the view that health is the reward for goodness and illness a punishment for sin as expounded or implied in the writings of Nahmanides, and of Ibn Ezra that the way to good health is to lead a good life. Third, an early midrashic source picked up again much later by Rabbi Israel Meir Kagan (the Hafetz Hayim) gives the argument from custodianship – since the body is divine property we have a duty to look after it well. So for Maimonides there is a prior duty to keep healthy, while for Nahmanides the prior requirement is to repent of sin. For the Hafetz Hayim, keeping the body healthy is an independent duty in its own right. These then are the differences in basic approach that may affect the emphases that different rabbis today place on health maintenance and promotion.