Any theoretical analysis on color reproduction of a color photographic or printing system requires as a first step the calculation of the relative amounts of a set of three dyes (cyan, magenta, and yellow) that compose a reproduced color of a certain chromaticity and lightness ( u, v, Y ). The amounts of a set of three dyes can be calculated uniquely when the spectral density distributions of the three dyes are known. The problem of calculating the amount of dye is reduced to solving simultaneous integral equations which are difficult to solve analytically. An algorithm for computer solution of the integral equations has been established using the Newton-Raphson technique. The computer program for metameric color mathching has been developed for the IBM-1130 computer in FORTRAN IV language. The results have been checked experimentally in dye solutions where the Lambert-Beer law holds to a fairly good approximation, and in color reflection-prints.