Purpose: To evaluate the osseointegration of mini-implants placed in grafted sinuses with lateral windows of two different dimensions. Materials and Methods: Sinus floor augmentation was performed in volunteers using a lateral window. The antrostomy was systematically prepared with a height of either 8 mm (large group) or 4 mm (small group). After 6 months of healing, mini-implants were placed in the grafted region. Biopsy specimens including the mini-implants were harvested 3 months after placement. Results: Twenty biopsy specimens, 10 from each group, were suitable for the histologic analysis. Similar amounts of new bone-to-implant contact were obtained in both the large (41.1% ± 19.5%) and the small (42.8% ± 13.2%) groups (P = .940). Small percentages of residues of xenograft were found in contact with the implant surface, with 0.6% ± 1.1% in the large group and 5.9% ± 9.5% in the small group (P = .098). The new bone density around the implants was 31.7% ± 8.2% and 34.0% ± 7.9% in the large and small groups, respectively (P = .623). Conclusion: The dimensions of the antrostomy did not influence the histologic healing of implants placed 6 months after sinus floor augmentation. Keywords: bone grafting, dental implants, osseointegration, sinus floor augmentation