This glasshouse study used an improved larval measurement procedure to evaluate the impact of transgenic pea, Pisum sativum L., seeds expressing α-amylase inhibitor (AI)-1 or -2 proteins on pea weevil, Bruchus pisorum L. Seeds of transgenic ‘Laura’ and ‘Greenfeast’ peas expressing α-(AI)-1 reduced pea weevil survival by 93–98%. Larval mortality occurred at an early instar. Conversely, in nontransgenic cultivars, ≈98–99% of the pea weevils emerged as adults. By measuring the head capsule size, we determined that larvae died at the first to early third instar in α-(AI)-1 transgenic peas, indicating that this inhibitor is highly effective in controlling this insect. By contrast, transgenic Laura and ‘Dundale’ expressing α-(AI)-2 did not affect pea weevil survival, but they did delay larval development. After 77 d of development, the head capsule size indicated that the larvae were still at the third instar stage in transgenic α-(AI)-2 peas, whereas adult bruchids had developed in the nontransgenic peas.