Resorption of the alveolar ridge may lead to ridge deformities that make dental implant placement difficult or impossible. Augmentation of the alveolar ridge may restore appropriate ridge form to allow implant placement. Forty-four patients with edentulous spaces completed this multicenter prospective trial to clinically and radiographically evaluate the efficacy of a bovine pericardium membrane and a particulate mineralized cancellous bone allograft in promoting lateral ridge augmentation. Overall, 38 of 44 patients (86.4%) were able to receive dental implants in the appropriate restoratively driven position 6 months after ridge augmentation. The mean gain in clinical ridge width after augmentation was 2.61 mm, while radiographically the mean gain in ridge width was 1.65 mm at a level 3 mm apical to the bony crest and 1.93 mm at a level 6 mm apical to the crest. On average, approximately 50% of the graft material added horizontally during surgery was displaced or resorbed during healing. Histomorphometric evaluation of cores taken from the augmented ridge at 6 months revealed that approximately 58% of the tissue volume was vital bone, with 12% residual allograft particles and 30% nonmineralized tissue.