Purpose: To investigate the effect of H2O2/HCl heat treatment on peri-implant bone formation in vivo. Materials and Methods: Twenty Ti-6Al-4V implants and 30 Ti-6Al-4V discs were used in this study. The implants and discs were separated into 2 groups: sandblasted and dual acid-etched group (control group) and sandblasted, dual acid-etched and H2O2/HCl heat-treated group (test group). Surface morphology, roughness, and crystal structure of the discs were analyzed by field-emission scanning electron microscopy, atomic force microscopy, and low angle X-ray diffractometry. The implants were inserted into the femurs of 10 adult white rabbits. Animals were injected with fluorescent bone labels at 1, 5, and 7 weeks following surgery to monitor progress of bone formation. Animals were euthanized 8 weeks postsurgery, and block biopsies were prepared for histologic and histometric analysis. Results: Microscopic evaluation showed the surfaces were quite irregular for both techniques; however, the test surface demonstrated consistently smaller surface irregularities. The differences in Sa values were significant (P = .022). No significant differences were found in the maximum peak-to-valley ratio values (P = .258). X-ray diffractometry analysis showed that titanium dioxide was found on the test surface. New bone was formed on both implant surfaces. The bone-implant contact pattern appeared to produce a broad-based direct contact. Test implants demonstrated 7.13% more bone to implant contact (P = .003) and 15.42% more bone to implant contact for 3 consecutive threads (P = .001) than control implants. Test implants demonstrated 37.04% more bone area 500 µm outside of implant threads (P = .004) and 51.97% more bone area within 3 consecutive threads (P = .001) than control implants. No significant differences were found in bone area within all implant threads between the two groups (P = .069). Conclusion: This study demonstrated that implants heat-treated with H2O2/HCl solution enhanced peri-implant bone formation. Schlagwörter: H2O2/HCl heat treatment, osseointegration, surface morphology, surface roughness, titanium dioxide