While considerable data have been published on the use of the osseointegration technique in the anterior region of the edentulous mouth, there remains scant information on its success in the posterior areas of either the maxillae or mandible. This prospective study was begun in the mid-1980s to test the effectiveness of this technique in the treatment of partially edentulous posterior areas of the maxillae and mandible, and in situations where the implant-supported prosthesis carries a significant portion of the total occlusal load. One hundred five implants were placed into 46 edentulous areas in 35 patients. After periods of loaded service ranging from 2.6 to 7.4 years (mean 5.2 years), of the 41 implants placed in maxillae, 40 (97.6%) remain in function, and of the 64 placed in mandibles, 59 (92.2%) remain in function. The overall implant survival rate of 94.3% suggests that partially edentulous areas in the posterior zones of either arch can be treated prosthodontically using osseointegrated implants with predictable success.