Structural and cytochemical organization of the basement membrane (BM) of the developing human brain at the embryonic period of prenatal ontogenesis was studied using light and electron microscopy and immunocytochemistry. Ultrastructural study has shown that the basement membranes of capillaries growing into the brain anlage are at the stage of formation (from the complete absence to the stage of broken membrane, without characteristic differentiation into layers). At the same time, BM of the brain surface looks sufficiently differentiated and prevents contacts of cells of the developing brain with meningocytes. These data are in contrast with results of immunocytochemical study, which show that the basement membranes (according to reactions for fibronectin, laminin, and type IV collagen) are clearly contoured around growing capillaries and, hence, exist from the very beginning of the intracerebral angiogenesis. The explanation of the established discrepancy between electron microscopic and cytochemical data seems to be searched for in spatial distribution and organization of BM components.