This article provides evidence on the effects of Bt corn on yield and insecticide productivity in the Philippines using a damage abatement framework that accounts for selection and endogeneity issues. We find that the yield-enhancing effect (or the damage-abating effect) of Bt corn is more strongly observed under poor weather conditions as compared to the effect in more “normal” weather. The value of using insecticides for controlling pests is significantly reduced when farmers already use Bt technology as a means of control.