Studies on the effects of gamma radiation on different life stages of Callosobruchus chinensis were carried out in a growth chamber at 30±1°C and 70±2% R.H. with a 12 : 12 hr light and dark cycle. Eggs (1-, 2-, 3-, 4-, and 5-day-old), larvae (7- and 10-day-old), mature pupae (one day before adult eclosion) along with adzuki beans and 1-day-old adults were exposed to gamma radiation from a ⁶⁰Co source. Complete mortality of the 1-day-old eggs was obtained by exposure to 12 Gy, and a dose of 40 Gy caused 100% mortality of the 7-day-old larvae after 24 hr of exposure. A dose of 640 Gy caused instant kill of the mature pupae and 1-day-old adults. The fecundity and fertility of adults irradiated either as mature pupae or 1-day-old adults decreased with the increase of the dose. Eggs, laid by females which had been exposed and/or had mates which had been exposed as mature pupae to 20 Gy or more, had negligible hatching rates. Complete sterility was obtained at 80 Gy in the 1-day-old adults. The sterilized males irradiated as 1-day-old at 80 Gy were capable of competing sexually with untreated ones. The percentage of egg hatch decreased as the ratio of sterile males to normal males increased, becoming less than 10% at the ratios of 9 : 1 and 15 : 1.