AbstractA method is presented for determining the relative amounts of Nb and Ge in thin films of approximately 1 μm thickness which have been deposited onto polycrystalline substrates. Quantitative X‐ray fluorescence is employed using an energy‐dispersive solid state detector and multichannel analyzer system. The principal problem encountered is one of calibrating the observed Ge/Nb intensity ratios in terms of atomic composition. We have used solution standards for comparison with the spectrum of selected dissolved films. The absolute compositions in the region of 25 atomic percent Ge are believed accurate to ±1 atomic percent abs