THE SCALY dermatoses which affect the scalp can be differentiated without difficulty in most instances, especially those which present concomitant lesions on the glabrous skin. In some cases, however, their clinical distinction is not easy, especially if the disease is limited to the scalp. In this study, biopsies were performed in a number of common squamous disorders which may affect the scalp, in an effort to appraise the diagnostic value of the histologic observations. There is a rather surprising paucity of information on the subject in various textbooks, even those which deal specifically with diseases of the hair and scalp. The material for the study consisted of histologic sections from 8 cases of circumscribed neurodermatitis (suboccipital dermatitis, lichen chronicus simplex), 13 of psoriasis, 14 of seborrheic dermatitis, 15 of chronic discoid lupus erythematosus and 5 of lichen planus. Since emphasis is placed on the histologic observations, clinical