The morphometric study of the corneal endothelium was carried out by means of specular microscopy prior to and for one year following laser trabeculoplasty (LTP) or laser iridotomy. A significant increase in the endothelial cell size was demonstrated in 6 months after trabeculoplasty and in 3 months following iridotomy. The magnitude of increase in cell size following laser iridotomy was significantly correlated with the amount of laser energy delivered to the eye. However, such correlation was not demonstrated following LTP where the applied energy was kept fairly constant among the present treated cases. The increase in cell size failed to correlate with clinical factors including IOP before and after laser therapy, age and the presence or absence of endothelial burn. The treatment protocols using reduced energy are indicated to minimize endothelial damage induced by LTP or laser iridotomy.