Purposes: The aim of this study was to assess the effectiveness of barrier membranes in bone augmentation through a systematic review of the literature. Materials and Methods: Electronic data banks and hand searching were used to find relevant articles on the reconstruction of localized bone defects published up to May 2011. Controlled animal and human studies with more than 4 weeks of follow-up were included; studies of periodontal lesions, extraction sockets, and maxillary sinus grafts were excluded. Applications of recombinant growth factor or assessments of membranes' effects on implant osseointegration were also considered exclusion criteria. Defects filled with bone graft/bone substitute material and covered with a membrane were considered the test group, while uncovered defects were considered the control group. Thereafter, human and animal studies were evaluated separately by meta-analysis. Results: Of the 3,986 articles found in the initial search, 34 studies met the inclusion criteria. Four animal studies concluded that the use of barrier membranes would increase the amount of vertical augmented bone (mean difference 0.32 mm; P = .006). Qualitative results regarding horizontal bone augmentation were controversial. Membranes do not increase the risk of improper healing, according to both human studies (odds ratio 5.67; P = .32) and animal studies (odds ratio 3.35; P = .12). Conclusion: There is limited evidence to support the effectiveness of barrier membranes in the treatment of bone deficiencies. Membranes do not increase postoperative infection, wound dehiscence, or membrane/bone graft exposure in either human or animal models. Because a majority of the results are based on animal studies, more randomized clinical trials are needed to objectively measure the efficacy of membranes in human bone augmentation. Keywords: bone engineering, bone regeneration, guided bone regeneration, guided tissue regeneration, nonresorbable membrane, resorbable membrane