Polymorphism of the major storage protein of sunflower seed, 11S globulin (helianthinin), was studed using the method of one-dimensional sodium dodecylsutphate polyacrilamide gel electrophoresis. The examined materials included seventeen accessions of annual and perennial Helianthus species, one accession of Tithonia sp. and six simple and complex interspecific hybrids. The helianthinin polypeptide compositiori differed considerably among the species of the genus. The annual and perennial species were most different. A numberof polypeptides were stable within the genus, the othèr ones were characterized by high variability. In the crosses of genetically close species, the polypeptide composition was inherited as a Mendelian character..However, by hybridization of distant species having non-homologous genomes (e.c., H. rigidus x H. annuus), poor polypeptide composition of hybrid protein was obtained. In hybrid seeds, only those polypeptides were expressed which were presents in both parents. This probably explains the seed non-viability in interspecific crosses of the genus Helianthus L.