The aim of the present trial is to compare in a horizontal guided bone regeneration clinical model, the allogenic-xenogenic combination to the autogenous-xenogenic combination. Edentulous ridges with less than 5 mm width were treated with guided bone regeneration using a glutaraldehyde cross-linked collagen membrane. Two graft combinations were used: autogenous-xenogenic (control group) or allogenic-xenogenic (test group). Ridge width measurements were recorded clinically and radiographically at 1, 3 and 5 mm from the ridge crest. Probe penetration was also recorded, and soft tissue healing was assessed during the follow-up visits. Core biopsies were retrieved for histological analysis. Four patients were recruited and randomly allocated to treatment groups with 12 sites of implant placement. 6 months after GBR surgery, all patients presented enough bone for implant placement. No difference was found between the groups in terms of clinical ridge width gain at the three levels of measurement. The mean percentage of graft resorption was 39.30 % and 29.31 % for control and test groups respectively, with no significant difference. In addition, no differences were found for probe penetration between the groups and no soft tissue complications occurred during follow-ups. Trends towards significance were evident for outcomes measurements. The protocol of this study should serve as a foundation for a larger-scale study with an improved population size.