Introduction of inorganic contaminants to bone during burial poses a serious problem for the interpretation of the levels of these elements in terms of ancient diet. The authors have found that the problem of non-uniform contamination may be reduced or even eliminated for some elements by removal of 1-3 mm. of the surface of the bone by physical abrasion. Whereas surface contamination on unabraded bone is readily visible in human femurs by scanning electron microscopy (SEM), there is no evidence of contamination after abrasion. This process of surface removal significantly reduces the levels of zinc, cadmium, potassium, aluminum, iron, and manganese, but has no effect on sodium, calcium, magnesium, strontium, and barium for these Woodland and Mississippian samples from west-central Illinois. The latter group of elements apparently survived burial without significant change. The former group of elements was affected by the soil environment, but at least for zinc, cadmium, potassium, and possibly iron, surface removal has returned the elemental proportions in the remainder of the bone to nearly biogenic levels. Analysis of variance between subgroups after cleaning shows differences in zinc and copper between sexes, in calcium, magnesium, and strontium over time, and in sodium and barium based on age at death.