Abstract : The purpose of this study was histological evaluation of horizontal ridge augmentation using xenograft with and without autogenous bone. The present split mouth study was conducted on 19 patients with insufficient width of alveolar ridge. The sites were randomly assigned into two groups, xenograft alone + A-PRF+ + Ti-d-PTFE membrane (Xenograft group) (n = 21) and the combined xenograft and autogenous bone (70-30) + Ti-d-PTFE membrane (Mix group) (n = 21). Nine months after the guided bone regeneration procedures and at the time of insertion of implants, biopsy of new bone was taken and was analyzed histologically. The obtained data were statistically analyzed. Amount of new formed bone and soft tissue was not statistically different between two groups (P > .05). However, the difference between two groups in terms of residual biomaterial was statistically significant (P= 0.000). Based on the results of this study, xenograft can successfully be used for horizontal augmentation of edentulous ridge, and adding autogenous bone to the granules of xenografts in 70-30 ratio does not significantly increase the quality of regenerated bone.