Unilateral, noninfectious, nontraumatic corneal endotheliopathy was noted in a 34-year-old man who had had blurred vision for five years without evidence of iridic disease or glaucoma. Ultrastructural studies demonstrated focal necrosis of the corneal endothelial cells, with desquamation of the cells into the anterior chamber. The corneal endothelium appeared to expand beneath the dying endothelial cells, indicating reendothelialization of the cornea. There was no epithelialization of the endothelium, as evidenced by the lack of keratin production or desmosome formation. Descemet's membrane was thickened with edema, a posterior collagenous layer, and fibrous, long-spacing collagen. These alterations in Descemet's membrane were similar to those described for other corneal dystrophies. It is proposed that this unilateral desquamating endotheliopathy represents an incipient form or a forme fruste of the iridocorneal endothelial syndrome.