The relationships of species were studied by making crosses in the genus Hordeum. Most of the crosses were between H. vulgare and one of the wild species. Embryo culture was necessary to produce most hybrids. The methods used for the preparation of the nutrient agar and for the excision of the embryos are given. Data on the seeds harvested, embryos transplanted, embryos germinated, and on the number of surviving plants are listed for 111 interspecific and six intergeneric crosses. In most of these crosses viable embryos were produced which later germinated and grew normally for a time but later died. Fourteen viable hybrids were obtained.