The specular microscope was used to study the corneal endothelium in three patients with essential iris atrophy and three patients with anterior mesodermal disorders with uncertain diagnose. Pleomorphic and enlarged endothelial cells were found to be typical for essential iris atrophy. The changes were also present in one eye with normal pressure. In the patients with other types of iridal disorder the endothelial cells were normal in form. In one of these patients high intraocular pressure and surgery had seemingly led to enlargement of the endothelial cells. According to our findings, the specular microscope is a useful aid differentiating essential iris atrophy from other disorders of the iris.