To develop a better surface conformation of titanium dental implants, we examined the in vitro biocompatibility of a thin natural apatite (NA) film deposited by laser ablation. Thin (2000-Å) hydroxyapatite (HA) and NA films were deposited on titanium discs using an ArF excimer laser operating at a repletion rate of 10 Hz and annealed by heating at 360°C for 1 h. Energy dispersive analysis of the NA film revealed peaks of Na and Mg in addition Ca and P. X-ray diffraction showed that crystalline HA was present in the HA and NA films. Primary mouse osteoblast grew faster and had higher alkaline phosphatase activity when grown in NA films than on HA films or a bare titanium surface. In addition, osteocalsin production by these cells was higher on HA and NA than bare titanium, but there was no significant difference between cells grown on HA and NA. Thus surface modification with NA film may contribute to successful osteoblast function and differentiation at titanium interface.