Purpose: The primary objective of this prospective cohort study was to evaluate primary and secondary implant stability values of implants placed into healed free fibula-reconstructed mandibles. The secondary objective was to investigate whether a correlation existed between primary implant stability and the quantity of cortical bone-implant contact and of cortical fibular bone in contact with the implants. Materials and Methods: The study participants are patients enrolled in a registered trial (No. CTRI/2012/07/002764). Patients with healed segmental mandibular reconstruction by means of free fibula flaps were chosen to undergo implant-supported dental rehabilitation. Preoperatively, computed tomography (CT) scans were used to measure the quality (density) of bone in Hounsfield units (HU). Implant stability quotients (ISQ) were obtained at the time of implant placement (primary), as well as 6 months later (secondary). The amount of cortical bone-to-implant contact (CBIC) was measured from postoperative panoramic radiographs using image analysis software (Image J). A paired t test was used to compare the mean primary and secondary ISQ values. Pearson correlation was used to determine the relationship between primary ISQ and CBIC. Statistical significance was set at the 5% level (P .05). Results: Of 54 patients (156 implants) who were enrolled, 35 (104 implants) were assessed. The reasons for exclusion were as follows: 11 patients (34 implants) had inadequate preoperative CT documentation, 7 patients (16 implants) had unreadable panoramic radiographs, and 1 patient (2 implants) had partial necrosis of the flap. The mean primary and secondary ISQ values were 78.1 (SD = 4.3) and 77.8 (SD = 4.6), respectively (P = .348). The mean density of cortical fibula bone was 1,344 HU (SD = 93.6). The mean CBIC was 3.7 mm (SD = 1.4). The study results showed a positive correlation between CBIC and implant stability (r = 0.274, P = .005). Conclusion: This study showed no differences in primary and secondary ISQ values of implants placed into the fibula. Implant stability quotients correlated positively with CBIC. Keywords: bone density, bone quality, dental rehabilitation, free fibula flap, implant stability, mandible reconstruction, removable prosthodontics, resonance frequency