The quantitative and qualitative losses in stored corn infested by Prostephanus truncatus (Horn), and stored for 20 wk at 30°C and 70% RH, were compared with those of Rhyzopertha 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, with P. truncatus peaking at 880 adults per 120 g corn by week 14, then declining slightly because of an exhausted food supply. R. dominica numbers increased to 550 adults per 120 g corn by week 14 and 1,300 adults per 120 g corn by week 20. P. truncatus dust production was significantly different from that for R. dominica ( P 0.05); only the P. truncatus treatment showed a difference in infection by Aspergillus glaucus group with a decrease after week 11 ( P < 0.005).