Life history of immature maize weevils,Sitophilus zeamaisMotschulsky, was studied at 10–40°C and 43–76% RH. The optimal quantity of corn for minimizing density effects and the optimal observation frequency for minimizing disturbance effects were determined at 30°C and 75% RH. The quantity of corn (32–256 g) provided to five females ovipositing for 24 h did not affect duration of development, but the number of progeny produced increased asymptotically as the quantity of corn provided increased. Frequency of observation (from 1- to 14-d intervals) did not affect duration of development or number of progeny produced. Using moisture contents measured in the life history study, an equation was developed for predicting equilibrium moisture content of corn from temperature and relative humidity. Duration of immature development did not vary with sex, but did vary with test. This suggests that insect strain or chemical composition of the corn must be included as factors in a model predicting effects of environment on duration of immature development. Survival from egg to adult emergence was greatest at 25°C. Sex ratio of emerging adults did not differ from 1:1. The number of multiply-infested kernels was low at all environmental conditions, and survival from egg to adult emergence in these kernels averaged 18%. Maximum daily rate of fecundity, duration of development, and number of progeny produced were optimal at 30°C and 75% RH. An index of environmental suitability indicated that 30°C and 75% RH was the optimal environment for growth of maize weevil populations on corn. Implications of the results for managing maize weevil populations are discussed.