The literature suggests that posterior polymorphous dystrophy (PPD) may show features such as iridocorneal adhesions, glassy membranes, and pupillary ectropion which are typically ascribed to the iridocorneal endothelial (ICE) syndrome. This complicates diagnosis. PPD, unlike ICE, is familial, and ICE, unlike PPD, is usually progressive and frequently complicated by glaucoma: thus it is important to distinguish between them. To determine whether this could be achieved by specular microscopy, since the posterior corneal surface is abnormal in both conditions, 57 cases of ICE and 44 of PPD were repeatedly examined and photographed with the specular microscope. Progressive and/or static morphological features of the corneal endothelium and Descemet's membrane were found that were specific for each condition. Specular microscopy can thus provide a definitive diagnosis of ICE or PPD even in uncertain cases.