We evaluated histochemically the distribution of proteoglycans in the trabecular tissue of goniodysgenetic (developmental) glaucoma. Nine trabecular tissue specimens obtained at trabeculectomy from seven patients with goniodysgenetic glaucoma were stained with either cuprolinic blue or cupromeronic blue in combination with a series of enzyme and nitrous acid treatments. Within the extracellular matrix of the trabecular meshwork, many cupromeronic blue- or cuprolinic blue-positive filaments were observed in association with collagen fibrils, basal lamina, and basal lamina-like material. The extracellular matrices of elastin-like fibers, fine fibrillar materials, and fine granular materials were free from any reaction products. The enzyme and nitrous acid treatments disclosed that the reaction products associated with collagen fibrils represented both chondroitin sulfate and dermatan sulfate types, while those with basal lamina and basal lamina-like material represented heparan sulfate-type proteoglycans. Extensive accumulations of basal lamina-like material contained a great deal of heparan sulfate-type proteoglycans in the thick subcanalicular tissue of goniodysgenetic glaucoma. These results indicate that the class and distribution of proteoglycans in the goniodysgenetic trabecular tissues are virtually the same as that in the normal tissues. However, the large accumulation of basal lamina-like material with heparan sulfate-type proteoglycans can be one of the causes of the intraocular pressure increase in goniodysgenetic glaucoma.