The exposure of adult male albino rats to lower environmental temperature (LET, 12°C) for 2 h inhibited the GABAergic activity in hypothalamus and corpus striatum. The treatment with diazepam (DZ) (5-10 mg/kg, i.p.) increased the hypothalamic GABAergic activity. But in cerebellum and corpus striatum the GABAergic activity was significantly increased only with higher dose (10 mg/kg) of DZ. The DZ-induced increase in cerebellar and striatal GABAergic activity was not significantly changed when DZ-treated rat was exposed to LET for 2 h. In hypothalamus, on the other hand, the DZ-induced increase in GABAergic activity was potentiated when DZ-treated rat was exposed to LET for 2 h. Further it may also be stated that the LET-induced inhibition of hypothalamic GABAergic activity was disinhibited, rather GABAergic activity was increased with the pretreatment of either dose of DZ. The cortical and thalamic GABA system remained unaffected with either this treatment or their cotreatment. Thus, the present results suggest that the LET or DZ-induced change in GABA system is altered when DZ-treated rat is exposed to LET depending on the specific region of the brain and dosage of the drug.