Historical Japanese fighting dogs subsequently produced a hybrid from Shikoku-ken and Western breeds, the Tosa-Kens. They are sometimes referred to as "Japanese mastiffs." The known contributing Western breeds were Bulldogs, Mastiffs, German pointers, and Great Danes; St.Bernards and Bull terriers are unaccountably reported. Tosa-Kens' familiar traits are stamina and fighting instincts. They are likely to be derived from Mastiffs. Formerly a fighting dog, nowadays it serves as a watchdog and pet requiring little grooming or exercise.

Also called Japanese Mastiff, Tosa, Tosa-Inu, Tosa-Token.