An in situ-toughened silicon carbide (ABC-SiC) has been examined in the as-processed condition, where the grain-boundary films are predominantly amorphous, and Following thermal exposure at a temperature of 1300 degrees C, where the films become fully crystalline. Previous work has shown that, at elevated temperatures (up to 1300 degrees C), after the grain-boundary films crystallize in situ, only a marginal reduction in strength, fracture toughness, and cyclic-fatigue crack-growth properties is observed, in comparison with those of the as processed microstructure at 25 degrees C, In the present study, the effect of such crystallization on the subsequent strength, toughness, and fatigue properties at 25 degrees C is examined. Little or no degradation is observed in the room-temperature properties with the crystallized grain-boundary films/phase; in fact, although the strength shows a small reduction (similar to 3%), the fracture toughness and fatigue-crack-growth threshold both increase by similar to 20%, compared with that of the as-processed structure with amorphons grain-boundary films.