Purpose: This systematic review examines the published findings on the clinical effectiveness and predictability of allogeneic bone blocks for the correction of alveolar ridge deformities to support dental implant placement in humans. Materials and Methods: A bibliographic search was conducted of the MEDLINE and EMBASE databases for studies in which allogeneic block grafts were used for alveolar bone augmentation. The search was limited to human studies in English-language publications between 1950 and September 2008. Data extraction included the following outcomes: (1) vertical and/or horizontal bone gain/loss, (2) graft failure rate and complications, and (3) implant survival rate. Results: The initial search identified 35 papers from the electronic databases, with nine publications meeting inclusion criteria: two case reports, six case series, and one prospective, multicenter, consecutive case series. No randomized controlled clinical trials were identified in the search. Observational studies (110 total patients) generally reported high rates of clinical graft incorporation (90% or greater) and implant survival (99% to 100%); however, the majority of reports involved selected defects in anterior regions with short-term follow-up (less than 3 years). Conclusion: Clinical evidence remains limited to case series and reports that differ with respect to alveolar ridge defect selection, treatment, and endpoints of therapy over short-term follow-up periods. Although case-based reports document the potential for allogeneic block grafts to support alveolar ridge augmentation and implant placement, insufficient evidence is available to establish treatment efficacy relative to graft incorporation, alveolar ridge augmentation, and long-term dental implant survival. Keywords: allograft, alveolar ridge, augmentation, bone, dental implant, onlay grafting