The aim of the present study was to perform a comparative histological and immunohistochemical evaluation of microvessel density (MVD), vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) expression in sinus augmentation using autologous bone alone or in combination to equine bone. Sixteen patients underwent sinus augmentation with autologous bone and a 50:50 mixture of autologous and equine bone. Control cores were harvested from pre-existing non-augmented bone under the sinus floor. The specimens were processed for immunohistochemistry. The greatest values of MVD were found in the sites grafted with autologous bone with significant differences between control vs autologous group (P < 0.01) and control vs autologous + equine group (P < 0.01). The higher and lower intensities of VEGF and NOS3 expression were prevalent in the sites grafted with autologous bone with significant differences with the controls (P < 0.05). No significant differences (P > 0.05) were found in the NOS1 expression among the groups. The results obtained showed that the mixture of autologous and equine bone was biocompatible, and its use was associated with new blood vessels ingrowth during healing, which has been found to be extremely important for bone formation.