Abstract: The influence of stress rupture notch sensitivity on crack growth rates have been investigated in GH36 iron-base superalloy discs.Stress rupture ductility improvement can eleminate stress rupture notch sensitivity and decrease the crack growth rates under creep condition or where creep is the dominant failure mode. But under fatigue condition, the crack growth raets are sensitive to material strength and independent of stress rupture notch sensitivity.Material strength improvement can significantly increase the resistance to low cycle fatigue crack growth.In order to improve the resistance to crack growth under creep, fatigue and creep/fatigue interacton, materials should be improved in both strength and ductility.