Type-A zeolite evenly covered with hydroxyapatite thin layers was prepared using hydrothermal treatment at 120degreesC for 8 h under autogenous pressure. The hydroxyapatite needlelike nanocrystals, 100-200 nm in diameter and 30 nm in thickness, were grown under the reaction between discharged Ca2+ ions from type-A zeolite and PO43-ions in (NH4)(3)PO4 solution. The preferential orientations. of the c-axis of hydroxyapatite crystals perpendicular to a zeolite surface were observed using transmission electron microscopy. The crystal structure of type-A zeolite was not destroyed under the reaction, but the surface morphology was changed only with complete covering of scaly hydroxyapatite particles.