The fluorescence decay time of naphthalene crystals has been measured as a function of sample thickness (1 μ-1 cm) and temperature (4.2°K-300°K) when excited in the first electronic state with UV pulses of short duration. A simple model is proposed to explain the decay mechanism, assuming constant quantum yield and oscillator strength and taking into account both Davydov-levels A and B. The reabsorption is found to be directly proportional to the temperature. The decay time of the lower Davydov-component can be measured directly as τA = (115 ± 5) nsec. The decay time of the higher level B is calculated from the dependence on the thickness as τB = (20 ± 10) nsec, and from the temperature dependence as TB= (30 ± 10) nsec.