Downy mildew resistance in the USDA inbred sunflower line RHA 419 was studied in F2 and test cross progenies from crosses with a susceptible line and with lines carrying known resistance genes. RHA 419 gives resistance to all races known at present, of type II, with frequent sporulation on cotyledons in seedling tests. The cross with a susceptible line indicated that one dominant gene imparted resistance to races 304 and 710. The progenies from crosses with lines carrying Pl5, Pl6 and Pl8 all showed segregation when tested with races 304, 710 and 730,generally agreeing with the hypothesis of two independent genes. It was concluded that RHA 419 provides a diversification of resistance and its use in breeding is discussed.