Effects on adult longevity, fecundity and fertility, as well as long-term effects on progeny were determined through oral exposure of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) adults to azadirachtin and methoxyfenozide. Both compounds reduced adult longevity by 2.3 d at the higher concentrations tested, but no significant differences were observed between sexes. Fecundity and fertility were significantly affected for both insecticides, although this effect was only dose-dependent for azadirachtin. The progeny from adults treated with azadirachtin or methoxyfenozide were only affected in percentage of pupation of eggs that successfully hatched, but no effects were observed in adult emergence of individuals that successfully pupated for either insecticide. In the second part of this study, each sex was exposed separately to methoxyfenozide by topical application or ingestion. Adult fecundity was more affected when moths were treated by ingestion than when treated topically, with a mean number eggs laid per female of 343 +/- 89 and 932 +/- 79, respectively. Finally, azadirachtin applied to pepper plants showed a significant oviposition deterrence activity on S. littoralis adults. However, when fecundity was scored for one additional day in females that had been previously exposed to pepper, Capsicum annum L., plants treated with this insecticide, the number of eggs laid per female did not differ significantly from that of controls. The effects of azadirachtin and methoxyfenozide on S. littoralis suggest changes in population dynamics of this pest in crops treated with these insecticides.