The mechanical behaviour from room temperature up to 1400 OC (strength, toughness, Young’s modulus) of a 3Al(2)O(3) . 2SiO(2) dense mullite material containing 0.2 wt% alkali has been studied. Microstructure has been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Toughness, bend strength and static Young’s modulus have been determined from room temperature up to 1400 degrees C. The influence of strain rate on fracture behaviour has been investigated and a correlation of the mechanical parameters to fractographic observations by SEM has been stated. A strong influence of loading rate on microstructural modifications during fracture at 1300 degrees C has been found.