Objective: Primary stability has a major impact on the long term success of dental implants. The aim of this study was to investigate the correlation of resonance frequency analysis (RFA) and insertion torque of self-tapping and non self-tapping implants and their respective differences in primary stability. Design: A group of 263 patients were treated with a total of 602 conically formed dental implants: 408 non self-tapping Ankylos® and 194 self-tapping Camlog®. The maximum insertion torque during implant placement was recorded. Resonance frequency, measured as the implant stability quotient (ISQ), was assessed once immediately after insertion and twice three months later. Results: Torque values of the non self-tapping implants were significantly higher than those in the self-tapping group (p=0.023). RFA did not show differences between the two groups (p=0.956), but a correlation between ISQ values after implantation and three months after implant placement was measured (r=0.712). Within the implant systems, no correlation between insertion torque and resonance frequency values could be determined (r=0.305). Conclusion: Our study indicates that ISQ values obtained from different implant systems are not comparable. The RFA does not appear suitable for evaluation of implant stability when used as a single method. Higher insertion torque of the non self-tapping Ankylos® implants appeared to confirm higher clinical primary stability. Keywords: resonance frequency analysis, insertion torque, primary stability, self-tapping implants, non self-tapping implants