Fracture toughness tests of tungsten and tungsten-rhenium alloy specimens were carried out at elevated temperatures. Temperature dependence of fracture toughness and effect of rhenium content on fracture toughness were investigated. Although fracture toughnesses of three kinds of specimens with rhenium contents of 0, 5 and 10 wt % were almost identical at room temperature, fracture toughness at elevated temperatures increased with increasing rhenium content. The brittle-ductile transition, similar to steels, and subsequent transition of the fracture mode from ductile dimple to intergranular were observed for all three kinds of specimens. With increasing rhenium content, the transition temperatures increased. A significant grain growth was found, not for tungsten-rhenium alloy specimens, but for a tungsten specimen without rhenium in a temperature range higher than the recrystallizing temperature, which resulted in transition of the fracture mode from dimple to intergranular.