A newly established murine vascular endothelial cell(EC) line, F-2C, has been previously reported to present a simple and useful in vitro angiogenesis model under serum free culture conditions, because of the spontanous induction of tubulogenesis, mimicking the morphology of the normal EC cultured on Matrigel. To learn more about this type of tubulogenesis, the effects of extracellular matix, including collagens(COL), laminine(LM) and fibronectin(FN) on this model were studied. The cell adhesiveness to the culture dish was promoted by the immobilized type I,III, and IV COL or LM and FN, but that to Type V COL was selectively inhibited. Further, the exogenous addition of type V COL to the culture markedly suppressed the cell growth and induced the fine flat networks of cellular cords in the cobblestone pappern, which were completely different from the original morphology of the tubes generated by F-2C. The electronmicroscopic studies of the networks showed that several F-2C cells formed a single hole inside the tube by connecting each other and the hole were filled with collagen fibers, which seemed to act as a template for the development of the network. The type V COL-induced network structure was finally remedelled again to be the original tubular structure in a few days. These observations suggest that the in vitro angiogenesis model generated by F-2C cells presents two different types of tubulogenesis and that the regulation of type V collagen fibers organization may give a clue of the differential EC tube formations.