Introduction: Over the years, several modifications have been made to the sinus augmentation technique and to the materials used. However, there is still controversy about the need for using a barrier concurrently with a graft in sinus augmentation procedures. On this basis, the aim of this randomized clinical study was to investigate the effect of resorbable collagen membrane over the osteotomy window on maxillary sinus augmentation healing. Materials and methods: Patients who required maxillary sinus augmentation were evaluated and selected to enter the study. After maxillary sinus grafting, each patient was randomly assigned to control (membrane over the osteotomy window) or test (no membrane) group. After 6 months, one bone biopsy was harvested from the lateral window and sent to the histology laboratory. The Mann-Whitney nonparametric test was used for comparing the two groups. P-value was set at 5%. Results: Eighteen patients entered the study and were randomly allocated in control (nine patients) or test group (nine patients). The histomorphometric measurements revealed that newly formed bone was 30.7% ± 15.5% of the total volume from the membrane group (control). The average percentage of connective tissue was 50.6% ± 18.7% and residual graft percentage was 18.4% ± 20.3%. On the other hand, data regarding the nonmembrane group (test) showed that the percentage of newly formed bone was 28.1% ± 19.4%. The mean percentage of connective tissues was 59.3% ± 15.4% and 12.6% ± 12.4% for the residual graft particles. No significant difference was detected in the histomorphometrical evaluation between the two groups. Discussion: Our results showed that, compared with sites not covered, the use of the membrane did not substantially increase the amount of vital bone over a period of 6 months. On the other hand, the use of membrane seems to reduce the proliferation of the connective tissue and the graft re-absorption rate. It is plausible that blood supply of maxillary sinus can play a role in such a result. Further studies are needed to explore whether the use of membrane could really be advantageous for the sinus augmentation procedure and to evaluate what influence this method can have on the amount and quality of reconstructed bone.