Edentulous areas of dog jaws were augmented with solid or porous particles of hydroxylapatite (HA) alone, or combined with either finely crushed autogenous bone or plaster of paris. At the end of the experiment (24 weeks), the augmented ridges were firm and stable and covered with healthy mucosa. The ridges augmented with only porous particles of HA demonstrated a greater amount of bone ingrowth compared with the solid, dense particles. The new bone formation occurred in those parts of the implants adjacent to the underlying alveolar bone. The addition of autogenous bone to the HA particles did not enhance bony deposition, and none of the autogenous bone chips survived for 24 weeks. The amount of new bone in the ridges augmented with plaster of paris and HA was similar to the other groups, and the plaster did not interfere with healing. There was evidence of resorption of the underlying cortical bone in many of the specimens.