Abstract: A zirconium base alloy is produced, having improved ductility after irradiation with fast neutrons, by heating in a protective atmosphere a zirconium base alloy containing precipitates in the form of at least one alloying element (e.g. Nb, Mo, Ni or Cr), which is soluble with the zirconium in the .beta. phase and insoluble therewith in the .alpha. phase, until the precipitates have dissolved, water quenching the zirconium base alloy to produce a fine martensitic structure supersaturated with the or each alloying element, working the zirconium base alloy in steps reducing the cross-sectional area 10% to 20% of the original cross-section, with annealing below recrystallization temperature for at least 10 minutes in the .alpha. phase between steps, until a total reduction of 70%-75% of the original cross-section is achieved, and then annealing the zirconium base alloy so that simultaneous recrystallization and precipitation of the or each alloying element occurs.