An osteoimplant composite comprising a plurality of particles of an inorganic material, a bone substitute material, a bone-derived material, or any combination thereof; and a polymer material with which the particles are combined. The composite is either naturally moldable or flowable, or it can be made moldable or settable. After implantation, the composite may be set to provide mechanical strength to the implant. The inventive composite have the advantage of being able to fill irregularly shape implantation site while at the same time being settable to provide the mechanical strength required for most orthopedic applications. The invention also provides methods of using and preparing the moldable and flowable composites.