Abstract: Creep rupture tests were carried out on a 18/8/3/1 Cr-Ni-MO-Ti stainless steel in both quenched and sigmatised conditions with a view to investigating the effect of sigma and carbide precipitation on the creep rupture properties of the modified 18/8 stainless steel. It is shown that at the three temperatures, 560℃, 600℃ and 685℃, specimens which were previously sigmatised 5 hours at 850℃ possess lower creep strength and greater creep rate as compared with those which were solution-treated at 1100℃. It is probable that sigma and carbide precipitation might have certain influence on the creep rupture properties of this particular steel.