A brief critical review is given of methods for determining the colorimetric description of reflecting fluorescent materials. A new method is described and its advantages are discussed. The method requires spectroradiometric calibrations of the spectrophotometer's source and detector systems and spectrophotometric measurement of total radiance factor, reflection radiance factor and conventional reflectance. A simple calculation then gives the total radiance factor of the fluorescent material for any specified illuminant. Experimental results with four strongly fluorescent samples indicate that the method has a colorimetric accuracy of about one unit in the CIE 1976L*U*V*color space.