A clinico-pathological study of reactive perforating collagenosis (RPC) is reported in seven adult siblings of both sexes in two unrelated consanguineous families from Kuwait. Although the primary defect in the skin of these patients is genetically determined, superficial trauma seems to be a triggering factor in most of the lesions. However, the regular occurrence of spontaneous lesions on the face in two patients and perniosis of the hands and feet in four other patients, together with the increased incidence on the exposed areas during the cold season, suggest an additive role for atmospheric cold. Experimental reproduction of RPC lesions was successful on the dorsa of the wrist and right middle finger respectively in two patients, while it failed twice on the covered areas. A significant finding was the absence of such lesions following deep incisional wounds, which suggests that the primary defect is in the pars papillaris of the dermis where a post-traumatic necrobiotic change starts off an RPC lesion.