Purpose: The aim of this prospective clinical trial was to compare peri-implant clinical and radiographic parameters following the placement of nonsubmerged two- and one-stage implants. Materials and Methods: Patients were randomly assigned to the IMZ group (20 patients receiving two IMZ two-stage implants in a one-stage procedure) or ITI group (20 patients receiving two ITI implants in the conventional one-stage procedure). The healing period was defined as an 18-week unloaded osseointegration period and a 1-year functional period during which maturation of bone took place. Twelve weeks after implant placement, fabrication of an overdenture with a bar-clip attachment system was started; it was placed at 18 weeks. Results: None of the implants were lost during the osseointegration period; one IMZ implant was removed during the functional period because of mobility. There was no significant difference in Gingival Index between the two groups at all evaluation periods. The mean bone loss during the functional period was 0.6 mm in both groups. A high number of healing abutments loosened in the IMZ group. Conclusion: Clinical and radiographic parameters of two-stage implants placed in a one-stage procedure and one-stage implants are comparable during the healing period. Healing abutments of the IMZ implant system loosen easily. Int J Prosthodont 2003;16:397–402.