Purpose: This study investigated the effect of the absence of estrogen on the process of implant osseointegration in the jaws of beagle dogs. Materials and Methods: Of eight beagle dogs, four underwent bilateral ovariectomy (OVX), and the other four constituted a control group. Twelve weeks postsurgery, XiVE implants (Dentsply) were placed in the second premolar site in the mandible and in the canine site in the maxilla. Zero, 4, 8, 12, and 16 weeks after implant placement, implant stability quotients (ISQs) were measured by resonance frequency analysis (RFA). Results: The blood estrogen levels 12 weeks postsurgery were 5.8 ± 1.8 pg/mL in the OVX group and 37.0 ± 2.9 pg/mL in the control group, which represents a significant decrease (P .01). The ISQ of maxillary implants in the OVX group 12 weeks after implant placement was 64.5 ± 1.7, and in the control group it was 74.3 ± 1.5; the ISQ was significantly reduced in the OVX group (.01 P .05). Conclusion: The results of this study indicate that the absence of estrogen induced by OVX in beagle dogs could reduce osseointegration around maxillary implants but has little influence in the mandible. Keywords: beagle dog, dental implants, estrogen deficiency, osseointegration, ovariectomy