BMP and activin membrane-bound inhibitor (BAMBI) is a transmembrane glycoprotein that is a pseudoreceptor of type 1 receptors. BAMBI structurally lacks intracellular serine/ threonine kinase domain but with an extracellular domain and a short cytoplasmic region that share sequence similarities with type 1 receptors, whose members have functions in signal transduction in various developing and pathological processes. BAMBI competes with the type 1 receptor, a receptor of the transforming growth factor-beta (TGF-beta), through functioning as negative regulators of TGF-beta by limiting the signaling range of the TGF-beta family during early embryogenesis. The expression of BAMBI can be induced by accumulated beta-catenin and BMP. The expression level of BAMBI was found aberrantly elevated in most colorectal and hepatocellular carcinomas relative to the corresponding non-cancerous tissues. It suggestes that beta-catenin and TGF-beta interfere growth arrest by inducing the expression of BAMBI, and this may contribute to colorectal and hepatocellular tumorigenesis.