The dermal histology and the regional draining superficial lymph node of a new mutant strain of hairless rats (ISh) were investigated. The homozygote ISh rat was characterized as having naked and wrinkled skin. The comedo-like cysts in the skin resembled human acne and vulgaris. Histopathologically, many Langerhans' cells positive for anti-protein kinase C type II antibody (PKC-II) were recognized in the epidermis. The superficial lymph nodes were significantly larger than those of the heterozygote. The paracortex of these lymph nodes was expanded and the number of Langerhans' cells mainly increased in these areas. These lymph node lesions were similar to those of human dermatopathic lymphadenopathy. The ISh rats should be a very useful animal model for studying dermatopathic lymphadenopathy in humans. Furthermore, they may be a valuable animal model for investigating the mechanisms of not only maturation, movement and migration of Langerhans' cells, but also of their function for antigen presentation.