AbstractPyridalyl is an insecticide of a novel chemical class (unclassified insecticides). Toxicity of pyridalyl to two insect pest species, Spodoptera litura and Frankliniella occidentalis, an insect predator, Orius stringicollis, and a pollinator, Bombus terrestris, was evaluated in the laboratory. The insecticidal activity of pyridalyl against S. litura was evaluated using the leaf‐dipping method. The potency of pyridalyl was highly effective against all development stages (2nd to 6th instar larvae) of S. litura. This compound was also evaluated against F. occidentalis using the direct spray method. For F. occidentalis, toxicity of pyridalyl was almost similar to that of acrinathrin, but greater than acrinathrin for adults. Then the toxicity of this product to the natural enemies, Orius stringicollis and the pollinating insect Bombus terrestris, was evaluated using the body‐dipping method or direct spray method. No acute toxicity of this product was observed on these non‐target insects. Moreover, the influence of pyridalyl to the nest of Bombus terrestris was evaluated using the direct spray to the inside of the nest. No apparent influence of this compound was observed by 21 days after treatment. The cytotoxicity of pyridalyl to the Sf9 insect cell line and the CHO‐K1 mammalian cell line was evaluated using the trypan‐blue exclusion method. High toxicity to the insect cell line, but almost no toxicity to the mammalian cell line, was observed. Thus, pyridalyl exhibited high selectivity in cytotoxicity between the insect and mammalian cell line as well as in insecticidal activity among insect species. We infer pyridalyl may be useful for IPM programs of greenhouse cultivation system. Arch. Insect Biochem. Physiol. 58:226–233, 2005. © 2005 Wiley‐Liss, Inc.