The quantitative and qualitative losses in stored corn infested byProstephanus truncatus(Horn), and stored for 20 wk at 30°C and 70% RH, were compared with those ofRhyzopertha dominica(F.). Treatments included insect-infested whole corn, uninfested whole corn plus ground corn (dockage), and uninfested whole corn. The quality assessment criteria included adult insect number, dust weight production, seed moisture content, changes in seed fat acidity value, germination, and microfloral infection of seeds. Both insect species multiplied quickly, withP. truncatuspeaking at 880 adults per 120 g corn by week 14, then declining slightly because of an exhausted food supply.R. dominicanumbers increased to 550 adults per 120 g corn by week 14 and 1,300 adults per 120 g corn by week 20.P. truncatusdust production was significantly different from that forR. dominica(P<0.005). Infested treatments had significantly different seed moisture content, fat acidity values, and bacterial infection of seeds compared with controls (P<0.005). Seed germination was significantly reduced for both species compared with controls (P0.05); only theP. truncatustreatment showed a difference in infection byAspergillus glaucusgroup with a decrease after week 11 (P<0.005).