A new analytical procedure was developed for estimating volume fractions of primary carbides in tool steels. The method utilizes electrolytic extraction of carbides, EDX analysis, and X-ray powder diffraction. Chemical compositions of individual carbide species are compared with the bulk carbide composition to find weight fractions of each species, and the volume fractions are calculated using the computed theoretical densities of the carbide species. Chemical composition and density of the matrix are also obtained as by-products of the procedure. The new procedure was successfully applied to AISI M2 high-speed steel and corresponding matrix tool steel in as-annealed and as-hardened conditions. It was shown that the etching process used in conventional metallography can cause overestimates of carbide volume fraction by 20 pct or more.