Purpose: To evaluate the changes in stability of immediately placed implants over a 6-month healing period relative to implants placed in native bone and to compare the stability of 2 different implant designs when placed as immediate implants in extraction sites. Materials and Methods: This prospective cohort study evaluated 3 implant patient populations. The control group (9 patients, 11 implants) required a single-stage, 1-piece, rough-surface implant (considered a "standard" implant) placed in nongrafted sites at least 6 months postextraction. The 2 experimental groups (25 patients, 28 implants) required extraction and immediate placement of either standard implants (12 patients) or tapered, self-tapping implants (13 patients). Immediate implant placement was carried out at the time of tooth extraction. Resonance frequency analysis (RFA), a measure of implant stability, was performed following implant placement at 2- to 4-week intervals for the first 16 weeks and at 24 weeks for immediate implants. Results: Placement protocol (control versus immediate placement) resulted in significant (P .001) differences in implant stability, even though there was no difference (P > .90) in initial, mechanical implant stability between these groups. The immediately placed implants had significantly greater reductions in stability, approximately 15%, from baseline to 4 weeks. Immediate implant stability was consistent with that of implants placed in native bone after 12 to 16 weeks. Implant design did not have a significant effect on stability. Conclusions: This study demonstrates that immediate placement protocols are viable options and that standard-design implants may provide levels of biologic stability similar to a tapered, self-tapping implant design in immediate placement protocols. Most importantly, this study documents high levels of metabolic activity in the supporting osseous tissue following immediate placement, which may extend time to restoration compared with traditional implant placement. (Clinical Trial) Schlagwörter: dental implants, implant stability, resonance frequency analysis, tooth extraction