Immediate loading of endosseous implants is becoming a widespread therapeutic procedure for the rehabilitation of patients with edentulous jaws. The purpose of this prospective clinical trial was to evaluate the long-term success rate of endosseous implants placed in the edentulous lower jaw and loaded on either the same day of surgery or the next day. Nineteen patients were enrolled in the study. Eleven patients, accounting for 64 implants, received their provisional prosthesis the same day of implant placement, and 8 patients, accounting for 52 implants, were rehabilitated the day after surgery. All patients were rehabilitated by a hybrid prosthesis supported by 5 to 6 Osseotite implants. Two implants failed in the group of patients who had their implants loaded the same day (96.9% success rate), whereas 1 implant failed in the other group (98.1% success rate). The overall implant success rate was 97.4%. All failures occurred within 2 months of function. No other complication was reported. The mean follow-up for this interim report was 37.8 +/- 16.5 months (range 8-65 months). Crestal bone loss was similar to that reported for standard delayed loading protocols. The results of this study suggest that the rehabilitation of the edentulous lower jaw by an immediate occlusally loaded implant-supported hybrid prosthesis is equally successful when loading is applied the same day or the day after implant placement. Immediate loading with 5 to 6 implant-supported prostheses represents a viable alternative treatment to classic delayed loading protocols.