Abstract: The effects of α-terthienyl (α-T) on the glutathione S-transferases(GSTs) were investigated in Helicoverpa armigera and Ostrinia furnacalis. Results indicated that near ultraviolet irradiation (300~400 nm) had no effects on GSTs activities in the control larvae of H. armigera and O.furnacalis both in vitro and in vivo. Treatment with high concentration of α-T inhibited the GSTs in vitro in H. armigera, but had no effects in O.furnacalis. Following topical administration, high doses of α-T increased the GSTs activities in vivo both in two insects. Upon ultraviolet irradiation, high concentration of α-T decreased the GSTs activities in vitro in H. armigera, But had no effects in O.furnacalis. After topical application, high dose of α-T reduced the activity in vivo in H. armigera but induced it in O.furnacalis. The differential response of GSTs against α-T in H. armigera and in O.furnacalis may be interpreted by their different sensitivities to α-T. And the variances in penetration, transportation, storage and metabolism of α-T may be also contributed to the differentiation.