HA (hydroxyapatite, Ca [subscript 10](PO[subscript 4])[subscript 6](OH)[subscript 2], Ca/P = 1.67) and composite TCP/HA (Tricalcium phosphate, Ca [subscript 3] (PO [subscript 4]) [subscript 2], Ca/P = 1.5) were synthesized in our laboratory from bovine bone ash or the waste from the manufacture of products derived from it and fabricated into porous bar and disc shaped specimens (30-34 v% porosity, flexural strength of 17 MPa, pore diameters <5-30 [mu]) for in vivo histological study and clinical trial, repectively. The histological results of the 3- and 6-month in vivo tests in canines were positive and successful. The clinical trials using titanium D-cages with HA inserts after 3-6 months were also proved positive, and with a satisfactory result. This also proved our belief that the practical limit of the smallest pore size for blood vessel or bone tissue ingrowth could be smaller than 100[mu] (macropore) in the case of resorbable HA ceramic with interconnected micro-to-mesopores (estimated as <1, 5-30 [mu]). To explore into a broader application, a coating of biological HA layer on Ti alloy implant was also studied and the results were discussed.