Austenite-ferrite steel of grade 03Kh13N10K5M3Yu2T with strain-induced unstable austenite is investigated. It is shown that the steel is quite suitable for the production of thin and very thin wire 0.15 – 0.8 mm in diameter with a high strength and satisfactory ductility. The optimum treatment of such wire includes water quenching from 1000°C, cold plastic deformation with a degree of 80%, and 1-h aging at 500°C. The strain-induced martensite is shown to possess a high susceptibility of strain aging.