In an article on vitamin A therapy in cases of disease Carleton and Steven 1 stated that it occurred to Peck that since the chief pathologic change is a follicular dyskeratosis, the disease might possibly be due to vitamin A deficiency. They listed follicular hyperkeratosis as one of the diseases associated with vitamin A deficiency which is amenable to vitamin A therapy. Weidman 2 has expressed the view that Darier's disease . . . is fundamentally and predominantly keratotic, as witness the original name, dyskeratosis follicularis. Weidman 3 wanted to stress the keratotic feature which may be follicular, but he could recall only 1 case in which the sheath of the follicle participated in the dyskeratosis. These statements induced me to review the literature and to study the biopsy material from 9 cases of typical keratosis follicularis in an attempt to determine whether the primary lesion of disease is a