We have used the electron microscopic immunogold technique to localize precisely various extracellular matrix components in human retinal vessels and Bruch's membrane. Collagen types IV and V, laminin, and heparan sulfate proteoglycan core protein were localized in basement membranes of retinal capillaries. In addition to the capillary basement membrane components, collagen types I and III and fibronectin were found in the basement membranes of retinal arterioles and venules. The basement membranes of choriocapillaries and retinal pigment epithelial cells in Bruch's membrane also showed a similar distribution of the retinal capillary basement membrane components. Both the inner and outer collagenous layers of Bruch's membrane contained collagen types I and III along with fibronectin, whereas collagen type VI was mostly limited to the central elastic lamina. The precise localization and distribution of various extracellular matrix components in human retinal vessels and Bruch's membrane may be important for understanding their normal function as well as their alteration in disease.