Two samples of protohistoric Iroquoians are found to show low values for bone formation indicators. Two southern Ontario ossuary samples, Kleinburg (1600 AD, N = 561) and Uxbridge (1490 +/- 80 AD, N = 457) are examined. Mean values for the cortical index (Barnett and Nordin, 1960) and percent cortical area (Garn, 1970) are consistently below expected normal values. Some of the lowest values may reflect the presence of a disease state. Nevertheless, it is argued that the results may indicate chronic dietary insufficiencies. Both absolute calcium intake and the calcium to phosphorous ratio are discussed as possible causative factors.