The coat protein (CP) gene of the potato virus Y (PVY) strain N605 has been cloned into a plant binary expression vector and introduced into the potato variety Bintje. The transformed lines, Bt6, that contained two copies of the CP gene showed complete resistance to the homologous strain PVY-N605 and a good resistance to the related strain PVY-O803 in the greenhouse. The good resistance of Bt6 to primary and secondary infections by PVY was confirmed in two successive field tests where the virus was transmitted by its natural aphid vector.