The photo-excitation spectral emission properties of 10 of the 14 NBS standard phosphor samples have been determined.Pressed tablets of the phosphors were excited by radiation from a mercury arc lamp, passing through a narrow band-pass filter to obtain either 2537A or 3650A excitation.The measurement system is described,correction of the data is discussed, and the spectral emission data are presented.Relative quantum efficiencies were calculated.The results are compared with measurements reported by two other laboratories.(Author).