The pigment glands of the cotton plant (Gossypium) produce a group of structurally related terpenoid aldehydes that protect the plant from herbivorous insects. Of these terpenoids, the most extensively studied is gossypol. Gossypolone, a compound closely related to gossypol, has been reported in the pigment glands but its activity against bollworm, Helicoverpa zea (Boddie), has not been reported. We report the effect on bollworm fed gossypol and gossypolone at concentrations of 0.06, 0.08, and 0.12% in an artificial diet. In previous studies, gossypol showed a hormetic effect when fed to tobacco budworm, Heliothis virescens (Fabricius), or Helicoverpa armigera (Hübner); in the present study gossypol also showed a hormetic effect when fed to bollworm. Gossypolone did not exhibit a hormetic effect at the concentrations tested, but pupae from larvae fed 0.12% gossypolone were significantly smaller than those fed the check diet or any of the diets with gossypol. Gossypol at the concentrations tested did not delay days to pupation, but in an earlier study gossypol at 0.16% delayed days to pupation from 13.9 ± 0.5 to 22.6 ± 1.0. In this study, gossypolone also delayed days to pupation but at a lower concentration [i.e., gossypolone at 0.12% delayed days to pupation from 13.3 ± 0.1 for the check to 20.8 ± 0.7 days]. A delay in days to pupation will reduce the number of generations that develop during a growing season, and may reduce larval survival. The biosynthesis of gossypolone may be due to a single gene. If so, increased expression of the gene could provide an overall increase in resistance to Heliothines pests of cotton.