Iron, demonstrated with the Prussian blue test, has been observed in the osteoid seams that accompany lamellar bone formation in 17 out of 19 diabetic cases, while it was absent in this location in all 60 nondiabetic persons used as controls. The Fe is homogeneously distributed throughout the osteoid, it is not particulate, and it is extracellular. This distinguishes it from hemosiderin-bound Fe which is both particulate and usually intracellular.