BACKGROUND: In the previous in vitro study, fluoride-modified, anodized porous titanium was proven to have enhanced its photo-induced hydrophilicity, which induced the hyperactivation of initial cell response. PURPOSE: The purpose of the present study was to investigate in vivo bone apposition during the early stages of osseointegration in rabbit tibiae. MATERIALS AND METHODS: Anodized porous titanium implants (TiU, TiUnite®, Nobel Biocare AB, Göteborg, Sweden) were modified with 0.175 wt% ammonium hydrogen fluoride solution (NH(4) F-HF(2) ). Twenty-four hours prior to the experiments, the surface-modified implants were ultraviolet-irradiated (modTiU). Blinded and unpackaged TiU implants were used as controls. Thereafter, the implants were placed in the rabbit tibial metaphyses and histomorphometrically analyzed at 2 and 6 weeks after insertion. RESULTS: ModTiU demonstrated a significantly greater degree of bone-to-metal contact than TiU after 2 and 6 weeks of healing. CONCLUSION: The results proved that the enhanced photo-induced hydrophilicity of the NH(4) F-HF(2) -modified anodized implants promoted bone apposition during the early stages of osseointegration.