Four intrabony lesions from four patients were studied. Presurgical measurements included clinical attachment level, degree of recession, probing pocket depth, Plaque Index, Gingival Index, and Sulcular Bleeding Index. These measurements were also taken at 6-month intervals after surgery. Surgery involved exposing the intrabony defects by a papillary preservation technique, planing, and placing blocks of coralline hydroxyapatite. Three biopsy specimens and one block section were removed from the treated lesions at various periods ranging from 6 to 36 months. Clinical and histologic observation provided evidence of osteogenesis around and through the coralline hydroxyapatite.