Infrared absorption spectra of over 500 pieces of gall stone were measured and analysis of gall stones by infrared spectra was established. This is the best method now known for the analyses of gall stones. Spectra were newly obtained for a group of calculi containing stearic acid, calcium stearate, triglyceride, and polysaccharide. Almost all of the gall stones are composed of a combination of such substances and cholesterol, calcium salt of bilirubin, calcium carbonate, calcium phosphate, and proteins, in various ratios and in variety of modes. A new classification has been proposed based on these chief components. It was also found that there is a vast difference in gall-stone components between urban and rural areas. Cholesterol, which is found in metropolitan area, is rare in rural villages and in its stead ratio of calcium stearate to calcium salt of bilirubin increases.