Recently, we developed a simple method for detecting a secretory signal sequence encoded by a cDNA fragment. In this study, we used this method to select cDNA clones encoding secretory proteins from a human full-length cDNA library. Full-sequencing analysis of the candidate clones revealed that one clone encoded a novel TGF-β superfamily protein. The clone encodes a protein of 308 amino acids of which the C-terminal region shows a characteristic feature of TGF-β superfamily proteins: seven conserved cysteine residues at the C-terminal preceded by a putative processing site composed of a basic amino acid repeat. The corresponding transcripts are highly expressed in the placenta, so the novel protein may play an important role in reproduction.