The 13 C/12 C ratio in human collagen was determined for 19 individuals from Hopewell sites in Wisconsin Illinois, and Ohio and compared with 27 new measurements from individuals of Archaic, Mississippian, and Late Woodland affiliation. Addiotional measuremente were made of elents in the food chain and on experimental animals fed on a diet of know composition containing maize. The similarity of the Hopewell measurements to those of nonmaize diets indicates that corn was of little importance in the Hopewell diet for those populations tested.