This report presents the current knowledge of Orobanche resistance in sunflower from the breeder’s standpoint and from the biochemists’ standpoint. The parasitic relations in Helianthus annuus / Orobanche cumana asso ciations differ in many respect from relations of other Orobanche spp. and their hosts. A major difficulty for the breeder is the fast development of new patho types of Orobanche cumana, which overcome the resistance of newly devel oped sunflower lines. The basis of increasing aggressiveness of Orobanche cumana pathotypes is discussed. Nevertheless, there is still large potential for resistance breeding in the genus Helianthus, since very different resistance fac tors are already known or shall be elucidated. A survey is presented of known resistance factors, such as low stimu lants, mechanical barriers and how they develop, phytoalexins, Orobanche seed germination inhibitors, inhibition of exoenzymes of the Orobanche radicles, in particular of polygalacturonase, which enables the penetration of Orobanche tissue into the host root along the middle lamellae. In this context an interesting new approach may be found in the polygalacturonase-inhibiting proteins occurring in cell walls, which inhibit the invasion of pathogenic fungi. The need for molecular biological studies will be stressed. Interdiscipli nary collaboration of breeders with biochemists and molecular biologists may lead to more advanced breeding strategies.