Purpose: This study was intended to investigate, through resonance frequency analysis (RFA), the stability of implants placed in an early loading protocol via the osteotome sinus floor elevation technique in the posterior maxilla. All implants featured a sandblasted/acid-etched active surface. Materials and Methods: An early loading protocol was considered for patients in whom implants with a sandblasted, large-grit/acid-etched active surface (SLActive) were placed in the posterior maxilla by the osteotome sinus floor elevation technique. Implant stability, which was measured by RFA at surgery and at weekly intervals for the following 6 weeks, was used as the most significant inclusion criterion. At the end of the stability observation period, only implants with a stability quotient of 65 or higher were loaded. Implants were followed for 2 years. Results: Twenty-seven patients received 42 implants, 40 of which were subjected to an early loading protocol 6 weeks after placement. Two years after loading, all 40 implants were surviving, without clinically or radiographically detectible complications. Conclusion: An early loading protocol can be used for SLActive implants placed in the posterior maxilla via the osteotome sinus floor elevation technique if their stability is confirmed by RFA. Keywords: dental implants, early loading, implant stability, resonance frequency analysis, sinus floor elevation, surface properties