The purpose of this investigation was to evaluate the technique of guided tissue regeneration on a clinical and histologic level for generating new bone adjacent to osseointegrated implants. Cylindrical, press-fitted, titanium plasma flame-coated implants were modified by a disk screwed onto the implant. After implant insertion, the disk-implant assembly was covered by an expanded polytetrafluoroethylene membrane. In one group, the space underneath the membrane was filled with hydroxylapatite granules; in the control group, no membrane was used. Clinical and histologic results demonstrate that the principle of guided tissue regeneration is applicable to osteogenesis in humans. Keywords: bone regeneration, guided tissue regeneration, osteogenesis, Teflon membrane