[en] Full grown male pupae of the cotton leaf worm, spodoptera littoralis boisd. were irradiated with 20 krad of gamma radiation. When the dose was delivered in one treatment or in 2 or 3 equal fractions, no significant differences were found concerning male emergence fertility, survival or female fecundity. Competitiveness of the irradiated males was not also affected by such dose fractionation. Male pupae were subjected to two low temperatures (5 degree and 15 degree C) as well as to normal rearing temperature (25 degree C) two days before irradiation with 5 or 20 krad. The results obtained showed that such temperature exposure did not affect the adult male emergence, fertility, longevity or female fecundity at the two doses tested. Exposure to 5 degree C showed the best male competitiveness at both doses. Slight differences in competitiveness between 15 and 25 degree C were observed. In general male competitiveness was better in case of 5 krad than at 20 krad, at all temperatures studied.4 tab