The effects of sunflower seed size on field performance of Anhandy?, ?Contisol? and ?C-33? cultivars were studied during four years (1981/82 to 1984/85). The seeds were sized into classes differing by 1/64? (0,4mm) in width and thickness. Results showed that seed size was related with seedling emergence, stand establishment and plant height, whereas there appears to be no yield consistent relation with seed size.