Posterior capsule opacification following extracapsular cataract extraction is a manifestation of migration of lens epithelial cells onto the posterior capsule. Collagen production by these epithelial cells results in white "fibrotic" opacities. These cells have myoblastic features and their contraction produces wrinkling of the posterior capsule resulting in visual distortion. A high magnification, in vivo specular microscopic study of human posterior capsules following extracapsular cataract extraction is described. In vivo findings correlate with histopathologic observations made on opacified posterior capsules. Lens epithelial cells migrate onto the posterior capsule and produce basement membrane and collagen. Collagen production is associated with a spindle-shaped appearance of the hyperplastic cells. This technique is useful for clinical research on posterior capsule opacification, including the evaluation of interventions designed to treat or prevent this complication.