The gecko Tarentola annularis, rejects skin allografts in a chronic manner, whereas the cutaneous response to tuberculin has the characteristics of mammalian delayed hypersensitivity reaction. Moreover, inoculation of gecko's spleen lymphocytes into skin of intact or whole-body--heavily irradiated allogeneic hosts, readily elicits a severe, local reaction (normal lymphocyte transfer reaction). The data indicate that slow skin graft rejection in T. annularis cannot be ascribed to either defective cellular immune reactivity or to the absence of strong antigenic disparity in the species.