The objective of this study was to investigate the in vitro and in vivo biological responses to carbonate apatite (cHA) in comparison to hydroxyapatite (HA). Spheres (400<ø>500 μm) of both materials were synthesized under 5°C (cHA) and 90°C (HA) and not sintered. The in vitro cytocompatibility was determined by the XTT assay, according to ISO 10993-5:2009, after exposure of MC3T3-E1 cells to the materials extracts. Ethics Commission on Teaching and Research in Animals approved this project (CEPA/NAL 193/10) and, subsequently, the biomaterials were grafted in the subcutaneous tissues of mice (n=15). After 1 and 3 weeks, five animals of each group were killed for samples removal containing biomaterials and surrounding tissues for histological examination. Semi-serial (5-μm thick) sections were cut and stained with Hematoxylin and Eosin (HE) and the presence of inflammatory infiltrates and biomaterials resorption were evaluated. The experimental group of 3 weeks didn’t show the presence of spheres of both biomaterials and few spheres were observed after 1 week. Histological analysis showed the granulation tissue around the biomaterials with the presence of multinucleated giant cells. After 3 weeks it was observed the presence of fibrous tissue around biomaterials and few inflammatory cells. No signals of tissue necrosis were observed in both groups in all experimental studied periods. Nanostructured carbonate apatite spheres are cytocompatible, biocompatible and present initial biosorption on the subcutaneous comparable to stoichiometric HA, indicating its suitability for further studies on regenerative medicine.