The absorption spectrum of gaseous plutonium hexafluoride was determined over the range of wavelengths from 2000 angstroms to 26,000 angstroms, and molar absorbancy indices were calculated. A test of the spectral method of analysis of plutonium hexafluoride in mixtures of plutonium hexafluoride and uranium hexafluoride was made. The results indicate that plutonium hexafluoride may be determined in mixtures containing uranium hexafluoride by use of a spectral method although care is required to pre-treat the cell windows to avoid reaction with plutonium hexafluoride.