Trabeculectomy specimens from 10 patients with congenital glaucoma were studied by electron microscopy. In all cases proliferation of fibrous connective tissue was found from the inner wall of Schlemm's canal. Accumulation of collagen fibres, sometimes of varied thickness and irregular striation, and agglomerations of microfibrillar material with the structure of collagen microfibrils were observed. This material formed basement membrane-like structures and 'shaggy' or fingerprint-like patterns. The ultrastructural examination of the trabecular meshwork revealed no significant differences between the morphological picture of primary congenital glaucoma and that found in Axenfeld and Rieger anomalies. Ultrastructural pictures of glaucoma cases examined in the present study converged also with those of juvenile glaucoma cases reported in literature, which may indicate the existence of a pathogenic factor common to these forms of glaucoma.