The cockroach, Blatta orientalis, is among one of the important domestic pests found in the semi-arid areas of Algeria. In this study, the insecticidal activity of spinosad, bioinsecticide, was tested against B. orientalis using different concentrations. Bioassays were done by topical application on newly emerged adult females under laboratory conditions. The results showed that the product exhibits a high level of toxicity with a dose-response relationship. The enzymatic analyses of the treated adults of B. orientalis with the determined LC₅₀ dose revealed a neurotoxic activity of spinosad, with an inhibition of acetylcholinesterase and a stimulation of the detoxification system that is interpreted by the increase of glutathione-S-transferase activity. In other experiments the compound was applied at LC50 on a newly emerged females and its effect was investigated on reproduction during the first gonadotrophic cycle (0, 2, 4 and 6 days) and the ovarian protein contents. The results showed that spinosad reduced the number of oocytes per paired ovaries, the size of basal oocytes and the ovarian protein contents.