A new photodensitometric technique (digital image processing, DIP) was performed to assess the bone mineral content of the metacarpal bone as a screening test for bone loss in 340 healthy or osteoporotic women as well as 35 steroid-dosed patients and 46 patients with chronic renal failure on hemodialysis. This procedure was compared with single photon absorptiometry and dual photon absorptiometry in terms of clinical value. Two bone mineral indexes, metacarpal index and sigma GS/D (the integrated bone mineral density of cortical and trabecular bone on a cross section in the middle of the second metacarpal bone), were equal to other methods in the quantification of decreases in bone mineral content due to aging in healthy or osteoporotic women. In addition, sigma GS/D was sensitive enough to detect decreases in bone mineral content in patients with vertebral fractures, on steroid therapy, and with chronic renal failure. Thus, sigma GS/D measured by DIP was shown to have clinical value as a tool in screening for decreased bone mineral content.