This investigation attempts to apply the concept of direct skeletal attachment via tissue ingrowth to the attachment of femoral head prostheses to the femur. Stainless steel (316L) canine femoral head prostheses with a ceramic coated stem were implanted into the femora of dogs and their results compared to those obtained by the impaction of stainless steel prostheses and acrylic-stabilized prostheses. The implants were tested in vivo for time periods ranging from 2 to 13 months, after which time the animals were sacrificed and the femora excised. The femora were sectioned with the implants in place and prepared for examination by light microscopy. Bone was in closer approximation to the ceramic coated implants than to the other two types of implantations. The uncoated and acrylic-stabilized implants were usually characterized by the presence of a relatively thick fibrous sequestering membrane.