Based upon the simplified theory of Kubelka and Munk a quantitative relationship for the fluorescent intensity, observed from either side of a plane parallel sheet of turbid material, has been derived. The fluorescing substance is assumed to be uniformly distributed throughout the bulk of the medium. The results obtained show that fluorescence measurements from either side have good linearity over a very wide range of concentrations of fluorescing substance. Measurements from either side are very nearly equivalent in this regard. As expected, the fluorescent intensity observed at the illuminated surface is higher than that observed at the exit plane. The results are intended mainly for use in the quantitative analysis of fluorescent substances dispersed in a turbid medium. Typical applications are thin-layer chromatography and electrophoresis.