Total resorption surface has been measured under ordinary light and polarized light in trabecular iliac crest bone from 57 healthy subjects and 40 patients with privational or malabsorption metabolic bone disease. Results obtained with the two methods were similar, although values for total resorption surface measured under polarized light were usually lower than those obtained under ordinary light in both groups of subjects studied. This most likely reflects the greater accuracy in the microscopic identification of resorption surface under polarized light.