Amphidiploid species of wheat have been produced from the following interspecific hybrid combinations: T. durum X monococcum (2n = 42), T. durum X timopheevi (2n = 56), T. turgidum X timopheevi (2n = 56), T. persicum X timopheevi (2n = 56), T. polonicum X timopheevi (2n = 56), T. polonicum X durum (2n = 56), T. vulgare X timopheevi (2n = 70), T. durum X vulgare (2n = 70). In the case of some of these, particularly the 56-chromosome types involving T. timopheevi and some member of the emmer series, several different strains of each species were used, so that a number of different strains of the amphidiploid were obtained. The 56-chromosome types are all interfertile, and are described elsewhere as vars. of a new species, T. soveticum Zhebrak. Hybrids between this species and T. vulgare, and between different amphidiploid species are highly sterile. In these hybrids certain dominant genes, such as that for spike color, still exhibit their dominance, even though present only once along with a double or triple dose of the recessive allele. Amphidiploids between species with homologous genomes, like T. polonicum-durum and T. vulgare-durum are much more sterile than those whose parents have non-homologous genomes. Their fertility can, however, be increased by selection.