Clinical specular microscopic examination of 17 patients with features common to the irido-corneal endothelial syndrome (including Chandler's syndrome, iris nevus syndrome, and essential iris atrophy) revealed pathognomonic endothelial changes and no areas of normal endothelial mosaic. Even in those patients with minimal anterior synechiae, gross central endothelial changes could be found, suggesting that the endothelial changes are primary and not secondary to the iris-corneal adhesions. Specular microscopy of the clinically-uninvolved contralateral eye in the patients revealed frequent endothelial-cell pleomorphism incommensurate with the patient's age. This study also confirmed the value of the specular microscopy in making qualitative endothelial observations.