Using immunofluorescent staining, we were able to characterize the changes in composition and distribution of the macromolecules making up the extracellular matrix of the lamina cribrosa of the glaucomatous human optic nerve head. In tissue adjacent to the glaucomatous cups, there was marked disorganization and loss of fibers of elastin within the cores of the cribriform plates. Collagen type VI, normally sparse, increased in quantity considerably throughout the lamina cribrosa in glaucomatous eyes with all degrees of damage. Collagen type IV and other basement membrane macromolecules appeared to extend into nerve bundles, presumably filling in spaces previously occupied by nerves. There was no appreciable change in the postlaminar region, which indicates the specificity of the extracellular matrix changes in the lamina cribrosa. Our results indicate that changes in the extracellular matrix play an important role in the progression of the glaucomatous process and may be a causative agent of the disease.