Healos T M , a new biodegradable calcium-phosphate mineralized matrix, is being developed for bone grafting. The mineral, a carbonated hydroxyapatite (HA), is prepared in a dispersion of collagen fibers, resulting in a uniform coating of mineral deposited onto collagen. The HA component is characterized and confirmed by X-ray powder diffraction analyses. In vitro studies show that Healos T M supports osteoblast adhesion and proliferation similar to extracellular matrix-coated or tissue culture-treated plastic. They also show that Healos T M can be a vehicle for the delivery of osteogenic growth factors. In vivo, Healos T M was observed to heal critical bone defects in both rat and rabbit models. In the rat parietal critical defect model, healing was observed radiographically as early as 14 days, and complete closure was seen at 28 days. No spontaneous healing was observed in the untreated defects. Histological evaluation revealed the implant to be biocompatible and infiltrated with abundant osteoblasts. New woven bone was formed from and over the cut edges of the defect and had surfaces that were lined with osteoblasts. When the defect was completely healed, the implant was replaced by new bone leaving no apparent residuals. In the rabbit segmental defect model, radiographic assessment showed healing, as early as 14 days, similar to the control group where the defects were treated with autogenous bone. An osteogenic growth factor containing formulation of Healos T M was also observed to induce healing in the rabbit segmental defect model.