Wurtzite (Ga,Mn)N films showing ferromagnetic behaviour at room temperature were successfully grown on sapphire(0 0 0 1) substrates by molecular beam epitaxy using ammonia as a nitrogen source. Magnetization measurements were carried out by a superconducting quantum interference device at the temperatures between 1.8 and 300 K with a magnetic field applied parallel to the film plane up to 7 T. The magnetic-field dependence of magnetization of a (Ga,Mn)N film at 300 K was ferromagnetic, while a GaN film showed Pauli paramagnetism-like behaviour. The Curie temperature of a (Ga,Mn)N film was estimated as 940 K. (C) 2002 Elsevier Science B.V. All rights reserved.