Abstract: A method for quantitatively analyzing solid mixtures of a crystalline ingredient and an excipient component in commercial pharmaceutical tablets by x-ray powder diffractometry using the intact tablet as is, without special sample preparation.The method comprises the steps of:irradiating the table with x-rays in a powder x-ray diffraction device and determining the integrated intensity of diffracted x-rays, I, at an angular range producing at least one x-ray diffraction line characteristic of said crystalline ingredient;determining the ratio of said value I to a diffracted x-ray intensity value, I.sub.o, obtained on a second compressed tablet consisting of said crystalline ingredient at said angular range; andcomparing the determined ratio I/I.sub.o to a set of predetermined standard values of said ratio for known mixtures of said crystalline ingredient and said excipient component to quantitate said crystalline ingredient in said first compressed tablet.