In 1991, several hairless offspring were found in our black haired KK (KK-C) mouse colony. This mutant, provisionally naming KK-rhino mouse was clinicopathologically and histopathologically investigated in a chronological manner. KK-rhino has a hairless trait and wrinkled and pimpled skin, which resemble the characteristics of the so-called rhino mouse. It was presumed from a preliminary mating examination that the trait of the KK-rhino mutant might be manifested by the [hrrh] gene. Other properties of this mutant might be inherited from the maternal KK-C line. KK-rhino mouse is a unique mouse strain which has two quite different traits, "rhino" and "diabetes".