A unique variant of Darier disease is described in which a patient was disabled by large, painful, cutaneous horns present on all extremities. The cornified lesions were distinguished by the presence of numerous corps ronds in the basal portion of the greatly hyperkeratotic stratum corneum, hypertrophic dermal villi containing enlarged capillaries, vacuolar dilatation of rough endoplasmic reticulum in sublacunar basal cells, unusually numerous Odland bodies in spinous cells adjacent to lacunae, and persistent attachment of tonofilaments to disrupted desmosomes. Complete separation of tonofilaments from intact desmosomes was not observed. Scanning electron microscopy revealed varied surface morphological appearances of corps ronds and of the epidermal cells covering the elongated dermal villi. The surface cells of cutaneous horns showed little tendency to desquamate.