Previous studies have shown that uranium is inhomogeneously distributed in excavated bones. It has been suggested that the higher concentrations of uranium found toward the outside of some bones may indicate that the uranium has been taken up by a diffusion process. This article briefly outlines a quantitative model of uranium uptake by diffusion and chemical reaction, and the measurement of uranium distributions in a number of samples. The authors explore the relationship of these distributions to environmental factors and to other diagenetic changes, compare them with the model, consider the implications of these results for the uranium series dating of bones, and suggest future directions in modeling uptake.