The ciliary zonules of the eye are composed of fibrillar and non-fibrillar components. Fibrils provide tensile strength and elasticity, whereas non-fibrillar components serve as a coating surrounding the fibrils. This coating behaves as a barrier to macromolecules. The present light and transmission electron microscopic (LM and TEM) study identified collagen IV as a novel component of this coating. Collagen IV was demonstrated by pre-embedding and postembedding immunohistochemical (IHC) techniques using monoclonal and polyclonal antibodies. The specificity of the polyclonal anticollagen IV antibody was verified by ELISA.