Abstract: Soluble fusion proteins of the TGF-? type III receptor and novel methods for their production are disclosed herein for the first time. The fusion proteins of the invention competitively inhibit the binding of members of the TGF-? superfamily to their cell-surface receptors. Also provided are methods for using these fusion proteins to modulate the biological activity of members of the TGF-? superfamily under in vitro or in vivo conditions, and to prevent or treat a variety of pathophysiological conditions associated with overproduction of TGF-? or mediated by altered signaling pathways of the inhibin/activin system.