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The use of extreme temperatures is one of the few chemical residue-free techniques available for control of pest species and has proven fast and effective in a variety of applications. We determined the upper and lower lethal temperatures for the brown treesnake. We also investigated whether gender, size, body condition and exposure time influenced survival at temperature extremes. Elevating snake core temperatures to 40°C and 41°C for one hour resulted in 99% mortality within seven days (40°C) and 100% mortality within one hour of exposure (41°C). Mortality decreased sharply to 51% for a one hour exposure to 39°C. Shorter, heavier snakes were more susceptible to extreme hot temperatures, but gender had no effect. The lower lethal temperature was established at a body temperature of -5°C held for one hour. Males were more susceptible to extreme cold than females, as were snakes with lower body condition. These results imply that brown treesnakes are slightly more vulnerable than many invertebrate pests, suggesting that hot thermal fumigation would not require exceptional treatments and should be feasible for shipments containing most non-biological materials and some biological ones (e.g., some live plants, grain), and cold thermal fumigation should be feasible for all materials tolerant of being frozen.