Purpose: Sinus floor elevation via the lateral window approach represents a reliable technique for augmenting bone volume in the atrophic posterior maxilla. However, controversy remains regarding the effect of placement of a barrier membrane over the lateral window. This histomorphometric meta-analysis sought to clarify the effect of barrier membranes in lateral window sinus augmentation. Materials and Methods: An electronic search of three databases and a hand search in implant-related journals for studies published through January 2013 in the English language was conducted. Randomized controlled trials, prospective human clinical studies, retrospective investigations, and case series reporting histomorphometric results after sinus elevation using the lateral window approach with at least six patients and a minimum followup period of 6 months were included. Results: The initial search yielded 1,040 articles, of which 94 were further evaluated for eligibility. Finally, 37 studies were chosen and separated into membrane (group 1) and no-membrane (group 2) groups. Similar vital bone formation was found in both groups: 32.36% for group 1 and 33.07% for group 2. Conclusion: Based upon this meta-analysis, the presence of a barrier membrane over the window does not influence the amount of vital bone formation after sinus augmentation. Additionally, the type of grafting material used and healing time did not influence the histomorphometric outcome. Keywords: dental implants, dental prosthesis, endosseous implants, implant-supported prosthesis, sinus floor augmentation