This research determined the percentage ofseed set and pollen tube growth in styles of six sunflower cultivars, under self-pollination conditions. Three days before anthesis, plants of the tested materiâl were bagged with paper bags to ensure selfp-ollination. The bagged plants were randomly divided in two equal groups. one was harvested after physiological maturity and seed set percentage was measured. From the other group, 48 hours after self-pollination, styles were removed and observed with microscope, in order to examine pollen tubes in the lower part. Results proved that strong relationship exists between sed set and penetrated styles percentage in the tested material. So, self-compatibility degree that is determined from seed set percentage under selfpollination, could also be determined by the percentage of penetrated styles from pollen tubes.