The effects of a novel organophosphorous pesticide, 2-butenoic acid-3-(diethoxy phosphinothionyl) ethyl ester (RPR-V) on glutathione S-transferases (GST), UDP-glucuronyl transferases (UDPGT) and the level of glutathione (GSH) were evaluated in rats after repeated oral administration at 33 microg kg(-1)day(-1) (low), 66 microg kg(-1)day(-1) (mid) and 99 microg kg(-1)day(-1) (high) for 90 days and at 28 days (withdrawal) post-treatment. GSH level and GST in kidney; GSH level in brain decreased significantly at mid and high doses on 45th and 90th day (P < 0.05). However, UDPGT activity in brain and kidney increased significantly at mid and high doses on 45th and 90th day (P < 0.05). Interestingly, the withdrawal study revealed that the effect was reversible 28 days after the treatment when all the enzymes reverted to levels close to those of controls. These results suggest that RPR-V has the potential to modulate the extrahepatic detoxifying enzymes and thereby interact with other physiological processes in the exposed organisms.