An implantable prosthetic valve (100) has an in situ formable supportstructure. The valve comprises a prosthetic valve (104), having a base and atleast one flow occluder. A first flexible component is incapable of retainingthe valve at a functional site in the arterial vasculature. The firstcomponent (126) extends proximally of the base of the valve. A second flexiblecomponent (128) is incapable of retaining the valve at a functional site inthe arterial vasculature. The second component extends distally of the base ofthe valve. At least one rigidity component (300) combines with at least one ofthe first and second flexible components to impart sufficient rigidity to thefirst or second components to retain the valve at the site.
