Objectives: The safety of the Otologics Fully-Implantable MET Ossicular Stimulator was assessed in adult patients with bilateral moderate to severe sensorineural hearing loss. Methods: Surgical implantation of the ossicular stimulator was performed. A repeated-measure, within-subjects design assessed safety and aided sound field thresholds and speech performances with the subject's own, appropriately fitted, walk-in hearing aid(s) and the Otologics Fully-Implantable MET Ossicular Stimulator. Results: Twenty patients were implanted and activated as part of the Phase I clinical trial. Results demonstrated 10-20 dB of functional gain across audiometric frequencies. Pure tone averages and monaural word recognition scores were slightly better for the walk-in-aided condition, while patient benefit scales favored the postoperative implant-aided conditions. Conclusion/Significance: Although monaural word scores and aided thresholds favored the walk-in-aided condition, preliminary results indicate that the Otologics MET Fully-Implantable Ossicular Stimulator is an alternative to currently available hearing aids in patients with sensorineural hearing loss.