In this study hydroxyapatite (HA) was coated by sol-gel method on Ti6Al4V alloy substrates: on micropolished surface and after titania (titanium oxide) treatment. Former shows the cracks and poor bonding of HA whereas latter shows coating without cracks and higher bonding strength. The higher bonding strength of HA coating in titania treated sample could be attributed to the increased roughness by titanium oxide layer.