Bone morphogenetic proteins (BMPs) are implicated in the regulation of morphogenesis and proliferation during embryogenesis and carcinogenesis. We have previously reported over-expression of BMP4 in diffuse-type gastric cancer cells. BMP signaling is regulated by tissue-specific expression of ligands and receptors as well as by secreted-type antagonists, such as CKTSF1B1 (Gremlin), CER1 (Cerberus 1), Noggin, SOSTDC1 (Ectodin), and Chordin. Here, we identified two novel genes related to CKTSF1B1 and CER1 by using bioinformatics. Two novel members of human CKTSF1B gene family were designated CKTSF1B2 (GREM2 or PRDC) and CKTSF1B3 (GREM3 or DANTE). FLJ21195 (BC046632.1) was the representative human CKTSF1B2 cDNA, and CKTSF1B2 gene was mapped to human chromosome 1q43. Human CKTSF1B2 showed 94.0% total amino-acid identity with mouse Cktsf1b2 (Prdc). FLJ38607 (AK095926.1) was the representative human CKTSF1B3 cDNA, and CKTSF1B3 gene was mapped to human chromosome 19p13.2. Human CKTSF1B3 showed 61.9% total amino-acid identity with mouse Cktsf1b2 (Dante). N-terminal signal peptide and DAN domain with nine cysteine residues were conserved among CKTSF1B1, CKTSF1B2, CKTSF1B3 and CER1. Phylogenetic analyses revealed that CKTSF1B2 was more related to CKTSF1B1, and that CKTSF1B3 was more related to CER1. CKTSF1B1, CKTSF1B2, CKTSF1B3 and CER1 constitute the CKTSF1B family among secreted-type cysteine knot superfamily proteins. This is the first report on identification and characterization of the human CKTSF1B2 and CKTSF1B3 genes.