Purpose: The aim of the study was to evaluate whether resonance frequency analysis (RFA) using a wireless transducer can be used to assess the primary stability of orthodontic mini-implants. Materials and Methods: Fifteen orthodontic mini-implants were placed in three ilium bone segments of country pigs. The wireless resonance frequency transducer was bonded to the head of the mini-implants, and RFA values of the mini-implants in bone were detected and converted into implant stability quotient (ISQ) values by the RFA monitor. In addition, the percussion test value, peri-implant radiographic bone density, and cortical bone thickness were measured. Results: The ISQ values of mini-implants correlated linearly with peri-implant radiographic bone density (r = 0.92, P .0001), cortical bone thickness (r = 0.90, P .0001), and percussion test values (r = -0.91, P .0001), respectively. In addition, by means of the calculation of 99% confidence intervals, the absolute values of the three correlation coefficients ranged from 0.61 to 0.98. Conclusion: This in vitro animal study showed that the presented RFA method using a wireless transducer might have potential to provide an alternative noninvasive assessment of the primary stability of an orthodontic mini-implant. Keywords: biomechanics, bone screws, dental implants, orthodontic appliance, torque