The transforming growth factor beta (TGF-beta) family is composed of a large group of growth and differentiation factors, including TGF-betas, activins, inhibins, Nodal, bone morphogenetic proteins (BMPs). These factors regulate a variety of cellular activities and are involved in many developmental and physiological processes. In recent years, we have been investigating the structure, function and signal transduction of these growth factors in the ovary and placenta.