Allylisothiocyanate is a volatile chemical used for insect fumigation. Because its mode of action is not fully understood, the insecticidal efficacy of AITC was investigated using dry and wet-table applications on the major stored-product insects Sitophilus oryzae (L.), Plodia interpunctella (Hübner), and Tribolium confusum Jacquelin Du Val. The LC50 values 72h after fumigation with AITC against S. oryzae adults, P. interpunctella larvae, T. confusum adults and T. confusum larvae were 2.0, 2.2, 3.7, and 4.7μlL−1 air, respectively. The complete mortality (100%) of all four insect pests was recorded after a 72-h exposure to AITC fumes at an atmospheric concentration of 11.5μlL−1 air, with results similar to those found with insects exposed to a recommended 5mgL−1 dose of phosphine. No differences were detected between the effects of AITC and PH3 on the morphology of mitochondria taken from the midgut and integument epithelial cells of treated T. confusum 3rd instar larvae. Rarefaction and vacuolization of the mitochondrial matrix were evident. The quantity of cristae and density of the electron matrix were also reduced. AITC has potential as a biodegradable and safe insect fumigant. The mitochondria alteration confirms the insecticidal effect of AITC, which may act on the respiratory system.