An investigation was made of the electroluminescence of epitaxial variable-gap Ga//1// minus //xAl//xSb p-n structures in which the forbidden band width of the solid-solution film increased smoothly away from the p-type GaSb substrate to the light-emitting boundary of the structure. The molar proportion of AlSb in the p-n junction region varied from 0. 04 to 0. 49, depending on the structure. The electroluminescence was found to be due to the recombination of electrons injected into the p-type region. The electroluminescence spectra consisted of one or more solid-solution bands with maxima at energies which increased with the forbidden band width in the p-type region of the p-n structure. The bands had a long tail on the long-wavelength side. The slope of this tail was used in estimating the diffusion-drift length of electrons in the variable-gap p-type region.