Trabeculectomy specimens from 11 patients with juvenile glaucoma were studied by electron microscopy and quantitatively evaluated. In all cases, large amounts of extracellular material arranged in a fingerprint-like pattern, resembling basement-membrane-like material (FBM) was found, similar to that described in steroid-induced glaucoma. This material was found mainly within the inner cribriform and outer corneoscleral regions of the trabecular meshwork, and caused the cribriform layer to be greatly thickened. FBM was also intimately associated with trabecular cells, which frequently appeared activated. In 3 cases, there was also an increase in fine fibrillar material which resembled that found in eyes with steroid-induced glaucoma. The amount of sheath-derived plaque material, which is increased in primary open angle glaucoma, was greatly increased in the subendothelial layer adjacent to Schlemm's canal.