This study addresses three aspects of anterior segment Nd:YAG laser treatment--acute endothelial damage, as assessed by endothelial specular photomicrography (ESP), acute and long-term intraocular pressure (IOP) changes, and long-term iridotomy patency. The acute ESP and IOP changes in 26 eyes (21 patients) after Nd:YAG laser iridotomies were compared to 39 eyes (37 patients) after Nd:YAG laser capsulotomy. Similar endothelial damage occurred in both groups, although less damage was noted in the group of 9 eyes in which capsulotomies were undertaken in the presence of an intraocular lens. In a parallel study 53 eyes (44 patients) were followed for a mean of 83 weeks (19 months) from the time of Nd:YAG iridotomy. There were no late closures and no late rises in IOP. The level of acute IOP rise after treatment did not predict long-term IOP. We conclude that Nd:YAG iridotomy is an effective procedure in the long-term, and that both iridotomy and capsulotomy are accompanied by noteworthy acute endothelial changes and intraocular pressure rises.