Purpose: To evaluate the clinical and histologic aspects of bone formation in maxillary sinus augmentation using macroporous biphasic calcium phosphate (MBCP) comprising hydroxyapatite/tricalcium phosphate (HA/TCP) 60/40 as bone-grafting material. Materials and Methods: A total of 10 patients and 12 sinuses grafted with MBCP in two-stage sinus augmentation were included in the present study. After a healing period of 6 months, bone core biopsies were harvested during implant insertion and evaluated under light microscopy. Results: The histologic examination showed that the MBCP particles were in close contact with new bone in all biopsies. Histomorphometric evaluation demonstrated that newly formed bone constituted 28.3% ± 2.7%, residual grafted material 27.3% ± 1.2%, and marrow spaces 45.9% ± 1.9%. Conclusions: Histologic investigation showed that the MBCP grafted particles were embedded and integrated in the newly formed bone; this bone was in close and tight contact with the biomaterial particles. Data from the preliminary results demonstrated that MBCP is a biocompatible and osteoconductive material that can be successfully used as a grafting material for sinus floor augmentation. Keywords: bone regeneration, biphasic calcium phosphate, human histology, sinus augmentation