The analysis of some cytogenetic parameters shows that the caffeine application on Favorit and PR64A83 cultivars of sunflower exercises a light mutagen effect on the cells of the root apex. At same time an intensification of the frequency of the ana-telophases with aberration takes place, especially of those with bridges, with retardatar and expelled chromosomes, but also of those with fragments, demonstrating the perturbation action that caffeine exercises on the division axle. The apparition of a great number of ana-telophases with fragments proves that this alkaloid induces ruptures at the chromosomal level (clastogenic effect).