The canine C blood group was determined by an agglutination reaction with a plant agglutinin extracted from the seeds of Clerodendron trichotomum (CTL). A positive agglutination reaction was classified as type C and a negative reaction as type c. In this study, the C phenotype and the gene frequency of C were examined in 377 dogs (224 purebred dogs of 29 breeds and 153 mongrel dogs) that were bred in Utsunomiya-city, Tochigi Prefecture. Phenotype C was less frequent than phenotype c in every purebred dog. A variation in C gene frequency was observed among the purebred dogs. The highest frequency of C allele was in the Yorkshire Terrier (0.202), followed by Beagle, Shiba (0.091), Maltese (0.085), Shi Tzu (0.051) and Shetland Sheepdog (0.036). The C blood group system as a genetic marker may provide useful information for bleed identification, genetic studies between breeds, and pedigree certification.