Several species of bats contain pigment granules within the scrotal skin, tunica vaginalis, or tunica albuginea surrounding the testis and/or epididymis. Seventy-two species of bats, representing 49 genera were examined for the presence of such pigmentation. Histological, chemical and spectrophotometric tests were performed and confirmed the pigment as melanin. Melanin was found only in the families Pteropidae, Megadermatidae, Myzopodidae and Vespertilionidae. A strong correlation exists between scrotal pigmentation and roosting in locations where the bats are exposed to solar radiation. Melanin pigmentation in the scrotal region appears to be an adaption protecting male germinal tissue from the harmful effects of ultraviolet radiation. In one species, Laoiu frons, melanin deposited within the scrotal skin appears to have a social/reproductive communication function.