Transforming growth factor β (TGF-β) superfamily signaling pathways are ubiquitous and essential regulators of cellular processes including proliferation, differentiation, migration, and survival, as well as physiological processes, including embryonic development, angiogenesis, and wound healing. Alterations in these pathways, including either germ-line or somatic mutations or alterations in the expression of members of these signaling pathways often result in human disease. Appropriate regulation of these pathways is required at all levels, particularly at the ligand level, with either a deficiency or an excess of specific TGF-β superfamily ligands resulting in human disease. TGF-β superfamily ligands and members of these TGF-β superfamily signaling pathways also have emerging roles as diagnostic, prognostic or predictive markers for human disease. Ongoing studies will enable targeting of TGF-β superfamily signaling pathways for the chemoprevention and treatment of human disease.