The stress-rupture properties of two heats of Hastelloy N tubing have been determined at 760°C in the irradiated and unirradiated conditions. Irradiation reduced the rupture life and the rupture strain but produced no detectable effects on the creep rate. The effects of irradiation are rationalized on the basis of the behavior of helium which is formed in the metal as a result of the 10B(n,α)7 Li reaction with thermal neutrons.