Farmers stock peanuts were either cleaned by removing foreign material and reducing loose-shell kernels (LSK) or left uncleaned before being treated with insecticides, stored, and artificially infested with several stored peanut insect pest species. The uncleaned peanuts contained only 2.8% foreign material. After 8 and 10 months the percentage of insect-damaged cracked pod kernels was 1.7 to 3.4 X greater in cleaned treated peanuts than in uncleaned treated peanuts, and there was a direct inverse relationship between the number of LSK and the percentage of damaged cracked pod kernels. After 8 and 10 months, the percentage of damaged cracked pod kernels in each class of peanuts, cleaned and uncleaned, was 1.6-5.7 X greater in peanuts treated with 52 ppm malathion than in peanuts treated with either 25 ppm chlorpyrifos-methyl or 25 ppm chlorpyrifos-methyl + 4 ppm methoprene. A significant difference in insect populations between cleaned and uncleaned peanuts occurred in untreated peanuts after two months, when almond moth and Indianmeal moth populations were greater in uncleaned peanuts. Thus, even a small amount of foreign material may provide a hospitable habitat for insect population growth. There were no significant differences in either insect damage or insect populations between chlorpyrifos-methyl and chlorpyrifos-methyl + methoprene.