Hydroxyapatite (HAP) has been used recently in orthopaedic fields as an aid in bone grafts following surgery of bone tumors and bony defect at the time of revision surgery, often promoting osteoconduction as a result. It seems reasonable to incorporate antibiotics into porous HAP beads to prevent local infection. This report describes in vitro and in vivo release behavior of cefotiam (CTM, 3.5 mg/bead) lcaded into HAP beads (9.3 mm in diameter). To control release rate of CTM, egg phosphatidylcholine (EPC) was also incorporated into the beads with the drug. Drug release from EPC-free HAP beads attained 100% in 3h in vitro, and with increasing EPC incorporated the release rate was sustained. In vivo study where the beads were implanted into rat femur muscle, the drug from EPC-free HAP beads was released almost 100% in 7h and the EPC incorporated bead gave an extended release. The release behavior of CTM in vivo study was compatible with temporal courses of serum level following implantation of beads. We conclude that EPC can be useful in controlling the release rate of the drug from HAP beads.