Protoplast fusion was carried out between Brevibacterium flavum and Corynebacterium glutamicum. For the protoplast fusion, various mutants were isolated from Brevibacterium Ravum ATCC 21493 and Corynebacterium gdutamicum ATCC 21831. The optimum conditions for protoplast fusion of these mutants were examined. In the present work, the authors obtained a fusant, MWF 9031, by the intergeneric protoplast fusion between Brevibacterium flavum 108-12S and Corynebacterium glutamicum 41-214A, which was excellent in L-arginine fermentation. Fusant MWF 9031 was found to accumulate a large amount of L-arginine reached 32.5 ㎎/㎖ with a medium containing 10% glucose. The fusant possessed intermediate characteristics between the parental strains and the stability was found to retain for 60 days.