This paper describes the development of an accurate, precise, and rapid analytical procedure using x-ray-fluorescence spectrometry for the determination of Nb, Ta, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Zr, and Sn in a wide variety of materials resulting from the processing of Ta-Nb-Sn slags to produce Ta-Nb oxides. The method involves evaporation of all the liquids to dryness, a 1:8 fusion of the solid materials with a flux consisting of Na-Li tetraborate and Na2CO3, and the addition of La oxide as a heavy absorber. With the use of a computer program, residual matrix effects are corrected for by influence-factor calculations.