This study examined the effects of a nanotubular surface treatment on an implant by anodic oxidation. Forty two screw-shaped implants were classified into 3 groups; machined surface (control group), nanotube formation on the machined surface (group N) and nanotube formation on the RBM surface (group RN). A total of 36 implants were inserted into a beagle femur. Two implants from each group were observed by scanning electron microscopy. Histomorphometric analyses were performed after 4 and 12 weeks. After 4 weeks, the average bone to implant contact (BIC) ratio of groups N and RN was significantly higher than that of the control group (P < .05). After 12 weeks, a nanotubular surface treatment showed a significantly higher BIC ratio only in the marrow space adjacent to the implant apex (P < .05). This in vivo study revealed the enhanced osseointegration of nanotubes.