Abstract The plant-derived insecticides have introduced a new concept in insecticide research. In response to insect attack, some plants can release volatile compounds in the atmosphere, which are lethal for the generalist insects. In this study, changes in the ultrastructure and electrical activity of mice sciatic nerve were examined after acute exposure to dimethyl disulphide (DMDS), a sulfur compound released from Allium porrum. Animals were exposed to 1/4 LC50 of DMDS (0.375 μl/l air) and tissue samples were evaluated by transmission electron microscopy. Degeneration in the myelin sheath and axon, decrease in the number of microtubules and neurofilaments, and evident damage in the mitochondria were observed. On the other hand, the effect of application of 1/4 LC50 of DMDS on the electrical activity of the sciatic nerve in mice showed that the number and amplitude of most of the spikes were less than that recorded in the control mice. The observed mammalian toxicity requires serious attention regarding a possible use of DMDS for pest control. Key words: Neuropathology, electrophysiology, dimethyl disulphide, sciatic nerve, mice.