The mucous membranes in close proximity to the cutaneous surface are the seat of pathological changes, for the most part identical with or modifications of the same diseases on the skin. To a great extent, the various involvements of the mucous surfaces have been described or at least mentioned in the text, as they were related to the various dermatoses. It only remains to give a resume of the conditions commonly affecting the conjunctiva and the eyelids, the nasal cavities, the external auditory, meatus, the mouth, the mucosa and skin of the penis, and vulva and vagina. The symptoms, etiology, pathology, differential diagnosis, prognosis and treatment of these disorders are the same as heretofore outlined for the coexisting cutaneous lesions, allowing for certain modifications due to location. A few of the affections of the mouth need more detailed description.