Genetic variation for resistance to a high temperature stress under saturated humidity was examined within and among three Drosophila buzzatii populations from Australia. Further, the acclimation of this species to high temperatures was tested by prelreating flies for a shorter, sublethal, time period under conditions that lead to expression of heat shock proteins. Genetic variation for temperature resistance was present among lines for flies either pretreated to high temperature or not. Pro-treating increased survival, with the benefit significantly higher if pretreating was performed 24 h rather than 96 h before exposure to the potentially lethal stress. For (lies pretreated at both times, resistance to heat stress was even greater. The lack of a significant treatment by line interaction term suggested that all lines were similarly plastic for acclimation following previous exposure(s) to a high temperature. Significantly more males survived the heat stress than females, and, within each sex, larger flies were generally more heat resistant than smaller ones. Additionally, the lines from the population that naturally encounters the highest temperatures were generally more resistant to high temperature stress.