A rapid method is described for isolating the globulin fraction (helianthinin) of sunflower seeds (Helianthus annum L.). The protein was characterized by chromatography and electrophoresis and compared with the globulin extracted from protein bodies. The native protein shows an apparent molecular weight of 300K, but, alternatively, a 190K band is present in some selfed lines of sunflower. Electrophoresis under denaturing conditions evidences four major components with molecular weights 39.2, 32.5, 25.6, and 23.2K, each containing two polypeptides and some minor polypeptides. In the 190K protein, the 32.9K component is absent. Isoelectric focusing indicated an heterogeneity of subunits within a pl range of 5.0-6.2 as confirmed by two-dimensional electrophoresis.