The effect of fluorescence saturation is caused by limited life-time of molecules in excited state, and appears as a non-linear dependence of detected fluorescence signal versus excitation intensity under laser pulsed irradiation of the sample. It is noticeable at conditions of 1024 exciting photons per second per square centimeter, which we usually have for laboratory laser fluorimeter. Spectroscopy of saturated fluorescence is a promising tool for studying such spectral molecular characteristics, as fluorescence life- time, absorption cross-section, constant of singlet-singlet annihilation, and their changes due to molecular interaction. The work presents the theory of the effect considering the cases of different intermolecular interaction (quenching mechanisms, singlet-singlet annihilation) and describes the experimental results on florescence saturation for several organic dyes in water.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.