Quantitative ratio of IAA/GA3 has been studied during the growth and development of different sunflower genotypes that represent a cms-Rf system. It was shown that the IAA/GA3 ratio was variable and it depended on ontoge netic stage, plant organ and genotype. Thus, the IAA/GA3 ratio the maximal value in the male sterile line while the minimal ratio was found in the restorer line RW 637 Rf. The highest IAA/GA3 ratio was registered in cotyledon leaves, which decreased subsequently in the course of ontogenesis. During reproduc tive stages, the ratio was higher in inflorescences than in leaves. The exoge nously applied gibberellic acid (GA3) increased the ratio in the fertile line. Specificity of the IAA/GA3 balance in the male sterility-fertility phenotype expression and in GA-induced pollen sterility is discussed.