Creep crack growth has been studied in Alloy 800H at 650 o C using CT-type specimens. The material, taken from a non-stressed inner sleeve of an expansion bellow in a chemical plant, was investigated for three conditions: (1) the as-received material (used for a long period of 72,000 h at temperatures of around 650 o C), (2) material which was prepared by subjecting the as-received material to heat treatment by holding for 0.5 h at 900 o C, followed by water quenching, and (3) material which had been subjected to a solution heat treatment consisting of holding for 0.5 h at 1100 o C, followed by water quenching. The creep crack growth rate was analyzed by using the parameter C * . There was no significant difference in creep crack growth rate between the two heat-treated materials. However, the creep crack growth rate of the as-received material was higher than that of the heat-treated materials because of the tendency for cracks to develop intergranularly in the as-received alloy.