The quenching of anthracene fluorescence in benzene solutions under high UV light intensity has been studied using a pulsed nitrogen laser (γ = 3371Å). It is shown to result from singlet-singlet and singlet-triplet annihilation. The overall annihilation rate constant is (3.5 ± 1.5) × 10 −10 cm −3 sec −1. Annihilation is due to dipole-dipole interaction of excited molecules.