Two new mammalian members (growth/differentiation factor 3 (GDF-3) and GDF-9) of the transforming growth factor-beta superfamily were identified using degenerate oligonucleotides corresponding to conserved regions among known family members. By Northern analysis, GDF-3 transcripts were detected primarily in adult bone marrow, spleen, thymus, and adipose tissue. In contrast, GDF-9 transcripts were detected only in the ovary. Based on their cDNA sequences, the predicted GDF-3 and GDF-9 polypeptides each contain a potential signal sequence for secretion, a putative tetrabasic proteolytic processing site, and a COOH-terminal region that shows significant homology to the known members of the transforming growth factor-beta superfamily. In the COOH-terminal region, GDF-3 and GDF-9 are most homologous to Xenopus Vg-1 (57%) and human bone morphogenetic protein 4 (34%), respectively. Unlike all previously described members of this superfamily, both GDF-3 and GDF-9 lack the conserved cysteine residue that is believed to form the sole disulfide linkage between subunits in other family members. These findings raise new possibilities regarding subunit interactions among members of this superfamily.