Broomrape (Orobanche cumana Wallr.) populations belonging to the new race F in Spain have overcome all known resistance genes, Or1 to Or5 , in cultivated sunflower (Helianthus annuus L.) and are spreading rapidly. Resistance to race F of this parasitic weed has been found in wild perennial species of Helianthus and has been introgressed into cultivated sunflower. The objective of this study was to characterize the inheritance of resistance genes in cultivated sunflower derived from wild perennial species H. divaricatus and H. grosseserratus, respectively. Crosses between resistant cultivated lines and the susceptible line P21 were made, and the F1's were resistant when evaluated for broomrape resistance using a highly virulent population of race F, indicating dominance of resistance genes. Comparison of resistance of the segregating populations, F2 and BC1F1, to both parents confirmed the dominance observed in the F1 and indicated that resistance is under the control of a single dominant gene. This dominance of resistance genes will greatly simplify the breeding for resistance.