While many studies have been conducted on possible effects of Bt-maize on beneficial arthropods, information on its effects on non-target pests of maize is scarce. Bt-maize has been planted in South Africa since 1998 for control of the maize stem borers, Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Pyralidae). No information is available on the possible effects that feeding on Bt-maize may have on other pests exposed to Cry1Ab protein when they attack seedlings or ears of Bt-maize. Important pests attacking maize seedlings are Heteronychus arator (Coleoptera: Scarabaeidae) and Somaticus angulatus (Coleoptera: Tenebrionidae), while Helicoverpa armigera (Lepidoptera: Noctuidae) is a sporadic pest of maize ears. The objectives of this study were to determine the effects of Bt-maize, expressing Cry1Ab protein, on these non-target pests. Laboratory studies in which larvae or adults of these species were fed with Bt and non-Bt-maize leaves or ears were conducted and mortality, growth, fecundity and fertility determined. Feeding on Bt-maize did not have a significant effect on any of these life-history parameters of H. arator or S. angulatus. In greenhouse and laboratory studies with H. armigera no larvae survived to the pupal stage on Bt-maize. This study showed that Cry1Ab-producing maize may protect the crop against H. armigera feeding damage. However, the likelihood of H. armigera becoming resistant to Cry1Ab protein over time, and it becoming an important secondary pest, is high.