The effects ofaw(0.90, 0.95, 0.98) and temperature (25°C, 30°C, 35°C) on aflatoxin production byAspergillus flavusandAspergillus parasiticusgrowing on irradiated maize seeds, were examined. Highest levels of aflatoxin were produced byA. parasitiousat 25°C and 0.98awand byA. flavusat 30°C at 0.95 and 0.98aw. At 0.90awtoxin production was consistently low for both species at all temperatures. Temperature cycling ofA. flavusbetween 25°C and 35°C each for 12 h resulted in higher aflatoxin synthesis than when incubated either at 25°C or 35°C.