The iridocorneal-endothelial (ICE) syndrome is characterised clinically by a "hammered-silver" appearance of the corneal endothelium, corneal failure, glaucoma, and iris destruction. Specular photomicroscopic studies of the corneal endothelium have demonstrated a population of abnormal cells termed "ICE cells." The purpose of this study was to define the histological appearances typical of this disease and in particular the ultrastructural morphology of the ICE cell. Thirty-five corneas, 11 trabeculectomy specimens, and 3 failed corneal grafts taken from patients with the ICE syndrome were examined by transmission and scanning electron microscopy. Comparison was made with seven normal corneas. Ten corneas and two trabeculectomy specimens demonstrated a population of well-differentiated cells with epithelial features such as desmosomes, tonofilaments, and microvilli. Other cell types identified were cells that resembled those of normal corneal endothelium, inflammatory cells, and cells with a fibroblast-like morphology. It seems likely that the epithelial cells of our specimens are the histological equivalent of the ICE cell seen by specular photomicroscopy. The other cell types may be either residual normal endothelial cells or else arise from secondary phenomena of various kinds.