In order to decrease the effects of contamination during burial, the authors removed about 1 mm from the surfaces of 50 human femurs from the Gibson (Middle Woodland), Ledders (Late Woodland), and Helton (Emergent Mississippian) sites. Elemental analysis of these abraded samples was compared with analysis of unabraded samples from the same femurs. Surface removal reduced levels of contaminative elements such as iron, aluminum, and manganese but had little or no effect on calcium, strontium, and barium. Analysis of variance was altered by cleaning. Many apparent differences between the sexes disappeared and must have been due to differential contamination. Other differences based on sex, age, site, or time are retained, improved, or initially uncovered by surface cleaning.