The effects of sunflower seed size on vigor of ?Anhandy?, ?Contisol? and ?C-33? cultivars were studied duriítg four years (1981/84). The seeds were sized into classes difering by 1/64? (0,4mm) in width and thickness; vigor was evaluated during six months each year, using speed of germination, accelerated aging and electrical condutivity. The results showed that seed of mean width classes were better in physiological quality than those of smallest one?s.