Described are expanded collagenous materials useful in hemostatic applications. Certain expanded collagenous materials can be prepared by treating a first collagenous material with an alkaline substance under conditions effective to expand the first collagenous material, recovering the expanded material, processing the expanded material to provide a foam, and chemically crosslinking the foam. Expanded materials can exhibit beneficial resilience, persistence and tissue generation characteristics when implanted, and can be used in the formation of highly porous medical implant bodies which can be compressed to fractions of their original volume and will thereafter substantially recover their original volume.