Egg cannibalism by Helicoverpa armigeraHubner (Lepidoptera: Noctuidae) larvae was studied in the laboratory and in the field. In laboratory experiments, first instars were exposed to increasing densities of H. armigera eggs on sorghum, Sorghum bicolor (L.) Moench, and pigeonpea, Cajanus cajan (L.) Millsp. The number of eggs eaten per larva increasedsignificantly as egg availability increased on both sorghum and pigeonpea. In small cages 21–37% of eggs were eaten on sorghum, 4–12%on pigeonpea. Plant feeding declinedsignificantly on both sorghum and pigeonpea asegg density increased. Cannibalism was greateron sorghum than on pigeonpea while plantfeeding was greater on pigeonpea than onsorghum. Only around 8% of eggs were eaten inlarger cages with sorghum. The response toincreasing egg availability in all experimentswas linear. Immunoassay with an anti-vitellinmonoclonal antibody showed that egg cannibalismoccurs on pigeonpea under field conditions.Seven percent of all larvae had egg protein intheir gut. Cannibalism may make a significantcontribution to H. armigera populationsuppression.