Hydroxyapatite (HA) has attracted much attention due to its biocompatibility and adsorption capability. The HA microtubes are highly attractive because they can provide improvement of functionality. It was found that HA microtubes were formed when alpha-tricalcium phosphate (alpha-TCP) was hydrothermally treated with addition of anatase. The fact that microtubes did not form under titania-free conditions indicated that titania played important roles to form microtubes.