The aim of this investigation was to evaluate successfully functioning implants stability in the partially edentulous mandibular molar sites by resonance frequency measurements. Resonance frequency measurement is more objective and clinically non-invasive method than any other methods had been used. In this study, $Osstell^{TM}$ (Integration Diagnostics, Sweden) was used. 15 patients ( 7 males, 8 females ) were received each 2 implants in their mandibular unilaterally partial edentulous molar sites. Total 30 implants were installed, 28 implants were $Br{\aa}nemark^{(R)}$ self-tapping fixtures(MK II, Nobel Biocare, Sweden) and 2 were $3i^{(R)}$(USA) self-tapping fixtures. Minimum of functional loading durations was 12 months and there were no significant marginal bone resorptions and peri-implant problems. From this test, the following results were drawn: 1. Mean ISQ values of implants in the first and second mandibular molar area were $73.66{\pm}4.45$, $71.93{\pm}3.41$, respectively. There was no significant difference between two groups(p>0.05). Also mean ISQ value of total sum was 72.8. 2. Mean ISQ values of implants in males and females group were $71.64{\pm}4.06$, $73.81{\pm}3.76$, respectively. And there was no significant difference between two group(p>0.05). 3. Correlation between implant lengths and ISQ values was weak(r=0.128).