Clinical specular microscopy (CSM) has recently been introduced as a means of qualitative and quantitative examination of the human corneal endothelium at high magnification. With the aid of CSM, a decline in endothelial cell density with age has been documented and several endothelial abnormalities from disease or trauma can be detected. Donor material for corneal grafting can be examined by CSM and keratoplasty procedures can be designed to decrease endothelial damage. Cataract surgical procedures can cause endothelial cell loss. According to most studies, intracapsular extraction causes less cell loss than does phacoemulsification, and cataract extraction with intraocular lens (IOL) insertion causes the greatest loss. Cell loss from IOL can be minimized by decreasing lens-corneal contact. Elevated intraocular pressure may lead to endothelial cell loss, as may therapy with epinephrine. Endothelial toxicity of other drugs and solutions can be studied by CSM. While long term studies are necessary to correlate the morphologic changes detected by CSM with future endothelial function, shortterm studies can be helpful in developing medical and surgical techniques that minimize corneal endothelial trauma.