Infrared spectroscopy was used in the qualitative analysis of 30 specimens of human biliary calculi. The spectrums of cholesterol, calcium bilirubinate, and calcium carbonate manifest (in certain areas of the spectrum) prominent and characteristic absorption bands that do not overlap. It is possible, therefore, to ascertain the presence of any 1 or 2, or all 3, of these constituents in a gallstone, that is, if the compound is present in more than trace quantity. The results of the study described in this paper verify the classification of gallstones on the basis of their chemical composition.