A wild Helianthus annuus L. population collected in Kansas, U.S.A., showed about 25% of its plants fully resistant to the herbicide imazethapyr applied in post-emergence at doses between 26.6 and 53.2 g.a.i./ha. Some plants survived treatments of 851.2 g.a.i./ha, i.e., 32 times the normal doses used in soybean. Artificially infected plants of this population with the parasitic weed species Orobanche cernua Loefl. (including O. cumana Wallr.) showed 100% of the plants susceptible. Artificially infected plants treated with imazethapyr in post-emergence on 40-day old plants killed most of the parasite nodules growing on the sunflower roots. The control of broomrape was 100% if the count only included the number of emerged broomrape shoots per plant. These results open the possibility of a new method for the control of Orobanche cernua in sunflower based on the use of resistance to this natural herbicide and the post-emergence treatment with imazethapyr.