Transforming growth factor β (TGF-β) and related ligands have potent effects on an enormous diversity of biological functions in all animals examined. Because of the strong conservation of TGF-β family ligand functions and signaling mechanisms, studies from multiple animal systems have yielded complementary and synergistic insights. In the nematode , early studies were instrumental in the elucidation of TGF-β family signaling mechanisms. Current studies in continue to identify new functions for the TGF-β family in this organism as well as new conserved mechanisms of regulation.