The intraspecific fusion frequencies obtained with the direct selection method on a semi-synthetic regeneration medium between strains of B. subtilis and B. licheniformis were distributed from 9.9 X 10(-2) to 4.5 X 10(-3), which was one or two orders higher than those of interspecific recombinations between B. subtilis and B. licheniformis. The regeneration media were also useful for selecting interspecific transformants from plasmid carrier to noncarrier. This selection could be used as a primary selection method for inter- and intraspecific recombinants obtained by protoplast fusion.