Surface escape of fluorescence is enhanced in crystals which strongly re-absorb their own fluorescence. This is investigated quantitatively for anthracene. The apparent fluorescence efficiency, measured by viewing the intensity of fluorescence transmitted through the crystal, is found to decrease as the depth of penetration of the excitant decreases. For photo-excitation this produces a fluorescence excitation spectrum since different exciting wavelengths penetrate different distances. The minima of the excitation spectrum correspond to absorption maxima. The maxima of the first absorption band of the crystal are hence found to occur at wavelengths 3960 A, 3740 A, 3540 A, 3370 A, and 3220 A.