Objective To analyze the molecular composition of type IV collagenous fibres in internal limiting membrane (ILM) of human retina. Methods ILM was surgically removed from retina and identified under phase-contrast and transmission electron microscopes. Monoclonal antibodies against different αchains (α1-α6) of type IV collagen were immuno-localized. Results α3, α4, and α5 chains of type IV collagen were immuno-localized in human retinal ILM, while α1, α2, and α6 chains could not be immuno-localized. Conclusion Type IV collagenous fibres in human retinal ILM are composed of α3, α4, and α5chains. (Chin J Ocul Fundus Dis，2004，20：364-368)