Titanium substrates were oxidized in oxygen or air at temperatures of 600 degrees -800 degreesC, then immersed in solutions of 2.0mM-20.7mM CaCl2 and 1.2mM-12.4mM KH2PO4 for aging periods of 0.5-10 d. The titanium surface was successfully coated with hydroxyapatite (HAP) when the substrates were oxidized in oxygen gas at 610 degreesC for 1 h and then aged in a solution of 200mM Ca2+ and 1.20mM PO43-. The Ca/P ratio of the surface coating increased toward its stoichiometric HAP value ((10)/(6)) as the aging time increased; the Ca/P ratio attained a value of 1.66 after 10 d.