Develops a theory for describing those diagenetic changes in bone that involve its interaction with groundwater, and considers three main processes as examples of such changes, namely the uptake of uranium, the dissolution of bone, and the increase of crystallinity of the bone mineral (carbonate hydroxyapatite or dahllite). Simple models of the chemistry involved are postulated in order to demonstrate the theory. The basic assumption is that the rate-limiting process in diagenetic change is the movement of solutes to, from, or within the bone. The main thrust of the article is to show how the physical structure of the bone itself, together with the hydrology of the burial site, interact to determine how water and its solutes move into, within, and from a bone during burial. This interaction can be of three kinds: diffusion, hydraulic flow, and recharge. All three types may operate together, and their relative importance depends on the extent to which the pore structure of a bone has been altered by diagenesis, as well as the type of chemical change taking place. It is shown that diffusion is usually the most common and important process, but that it is possible to predict the hydrological regimes in which other mechanisms dominate. Knowledge of site hydrology (mainly the specification of soil structure and moisture variation), the physical state of the bone, and the chemistry of the diagenetic process can provide estimates for the rate and manner of the particular diagenetic process. Such estimates agree with observation.