The taste responses to the "umami" substances such as monosodium glutamate (MSG), GMP, and IMP were recorded from the chorda tympani nerve of mongrel dogs and beagles. A large synergism was observed between MSG and two species of nucleotides (GMP and IMP) in most mongrel dogs and between MSG and three species of nucleotides (GMP, IMP, and AMP) in beagles. The extent of the synergism between MSG and the nucleotides was much larger than that observed in any other animals examined except for humans. In the presence of GMP, the response magnitude of the chorda tympani nerve to MSG was increased but that to NaCl, HCl, sucrose, quinine, and glycine was unchanged. It was concluded that the canine taste responses to the umami substances closely resemble those in humans, and the dog is a suitable animal model for studies on the responses to the umami substances.