Absolute quantum efficiencies of several inorganic phosphors have been measured with excitation in the spectral region 1500 to 2900 A. In contrast to the results of Butaeva and Fabrikant no efficiencies greater than unity were found. The measurements were made by comparing excitation spectra with absolute quantum efficiency determinations under excitation by 2537-A mercury resonance radiation. A method for determining quantum efficiencies, using only relative radiance measurements on a series of phosphors having different activator concentrations, was used to confirm the results obtained with vacuum ultraviolet excitation.