The physical basis for predicting the long-term creep strengths and lifetimes at application temperatures using

creep parameters determined from short-term creep tests is investigated for complex creep resistant engineering

alloys. It is shown that the seemingly unpredictable stress and temperature dependence of minimum creep rate of

such alloys can be rationalised using an approach based on the new power law creep equation that incorporate the

tensile strength. This is demonstrated using the tensile and creep data measured for two completely different types

of alloys: steel 11Cr-2W-0.4Mo-1Cu-Nb-V and Ni base superalloy 15Cr-28Co-4Mo-2.5Ti-3Al. For both alloys,

the stress exponent n determined does not depend on temperature and activation energy of creep does not depend

on stress. Consequently, it becomes possible to use the new power law creep equation in combination with the

Monkman-Grant relationship to predict the long term creep rupture strengths and lifetimes and microstructure sta-

bility of the two alloys from short term creep test data. The implications of the results for creep mechanism iden-

tification and future microstructure analysis are discussed.