Immunogold labeling was applied at the ultrastructural level to the identification of collagen types I, II, III, V, and VI in the human trabecular meshwork obtained from 11 surgically enucleated globes. Both London resin white embedding and cryoultramicrotomy were used, and for types V and VI, the latter provided more sensitive localization. Type II collagen was not identified. Types I and III were localized to the striated collagen fibrils of the trabecular core, the basement membrane of the trabecular beams, and loose aggregates in the juxtacanalicular tissue. Types V and VI formed a fine network around the striated fibrils in the trabecular cores and linkage strands to the basement membranes. The outer wall of Schlemm's canal contained collagens I, III, V, and VI. Long-spacing collagen and elastin-like material did not label with any of the antibodies used in this study.