Spinal cord-derived growth factor (SCDGF)/platelet-derived growth factor (PDGF)-C/fallotein has a unique two domain structure, as it contains two regions homologous to CUB and PDGF/vascular endothelial growth factor (VEGF) domains. In this study, we isolated a novel gene homologous to SCDGF/PDGF-C/fallotein, and named SCDGF-B. The culture supernatant of CHO-K1 cells stably transfected with SCDGF-B showed mitogenic activity as SCDGF/PDGF-C/fallotein did. Although SCDGF-B and SCDGF/PDGF-C/fallotein might be the members of the PDGF/VEGF superfamily of growth factors, they were categorized into a new subfamily in addition to PDGF and VEGF subfamilies.