The effects of ^(60)Co-γ radiation on the change of composition and susceptibility to soft rot during the storage of sweetpotatoes and the radioresistance of spores of the soft rot fungus were investigated and the following results were obtained. 1) Gamma-irradiation of sweetpotatoes caused the increase in water-soluble sugar content and the decrease in ascorbic acid content during the storage. 2) The rate of oxygen uptake in sweetpotato slices becomes higher as the dose increases. But the oxygen uptake in slices irradiated with higher doses decreases along with the color change as the time passes. 3) Irradiation with high doses (above 2.5×10^5 rad) brought about the increased susceptibility to soft rot decay as the chilling injury did in the storage of sweetpotatoes. 4) Average lethal dose for the spores of Rhizopus nigricans was 3.0×10^5 rad and the complete death required the level of 1.25×10^6 rad.