Pre- and post-operative endothelial specular photo-microscopy was performed on 46 eyes of 29 patients who had been randomly assigned to iridotomy with the Nd:YAG or the dye laser, or to surgical peripheral iridectomy for the relief of pupil block glaucoma. Localised damage to the endothelium was observed in two eyes following Nd:YAG laser iridotomy and in one eye following dye laser iridotomy. No endothelial changes were recognised after surgical peripheral iridectomy. Central corneal endothelial cell densities remained unchanged following all procedures.