It is expected that gamma (γ) and ultraviolet (UV) rays are applicable to sterilize agricultural products for reducing storage losses. In practical application, D_<10>- and D_<99.9>-value in γand UV irradiation have been used as sterilization indices. However, our preliminary results showed that these survival curves were exponential having a shoulder at the beginning and a tailing at the end in many strains of molds. This suggests the difficulty in assessing a sterilization level accurately using these indices. The survival curves of several molds infecting agricultural products for γ irradiation were simulated by a multihit theory in molecular radiation biology. On the other hand, the effect of UV irradiation on the survival curves was simulated by a modified multihit theory considering the decrease in UV-intensity in liquid suspensions due to Lambert's law. It was found that the models based on a multihit theory well simulated the effects of γ and UV irradiation. Among molds tried in this study, the four hits model best fited to the observed data in both cases of Ascomycetes and Phycomycetes. These results demonstrated that D_<10>- and L-values, instead of conventional indices based on D_<10>-and D_<99.9>-values, should be used to assess the sterilization level accurately. To obtain more reliable measurement, a target area and a hit number, a parameter of penetration in UV- sterilization should be taken into considerations.