The aim of this experimental study was to evaluate the use of autogenous bone harvested during preparation of implant sites in combination with resorbable membranes for vertical ridge augmentation under 2 different defect site conditions. Combined vertical/horizontal alveolar bone defects were created by experimentally induced periodontal infections around all premolar teeth in the mandibles of 3 dogs (group 1). In another 3 dogs, fresh surgical defects were created after extraction of all premolar teeth in the mandibles (group 2). In all dogs, 2 implants were placed on each side of the mandible into the defect areas. One implant on each side of the mandible received augmentation with autogenous bone particles, and both implants on one side of the mandible were covered with polylactic acid membranes. After 5 months, the material was evaluated histologically. There was a small but significant increase in bone regeneration in the defects augmented with bone particles with and without membrane coverage in group 1. In group 2, no significant difference was seen between the controls and the augmented sites. The major limiting effect for bone regeneration appeared to be insufficient stability of the bone material to withstand the overlying soft tissue pressure. It was concluded that the placement of autogenous bone particles, either with or without membrane coverage, had little effect on the regeneration of peri-implant bone defects. Keywords: artificial membranes, bone regeneration, bone transplantation, dental implants, guided tissue regeneration, membranes, polymers