For the replacement and regeneration of hard tissues, hydroxyapatite (HA) has been considered to be one of the most promising biomaterials. To develop new potential HA-based nanofibers, microfibrous composite membranes were first prepared by electrospinning from gelatin calcium phosphate (CaP) sol blend solutions of various concentrations of CaP sol. The resulting fibers exhibited a fully interconnected porous structure and their average diameter varied from 1.09 +/- 0.24 pm to 1.44 +/- 0.17 mu m according to the CaP sol content. For the fabrication of HA nanofibers, the thermal treatment of microfibrous composite membrane was carried out. After the thermal treatment at 800 degrees C, the average fiber diameter of GECP20 composite membrane significantly reduced from 1.21 +/- 0.21 pm to 400 +/- 52 nm, which may be caused by the elimination of gelatin due to the thermal treatment. ATR-FTIR, EDX, XRD and XRF analyses confirmed that the HA nanofibers could be produced by combining the electrospinning and thermal treatment methods in the sol gel process. These HA nanofibers showed the same crystalline phase with that of the stoichiometric HA. In addition, the results from simulated body fluid immersion (SBF) test and cell viability assay showed the improved in vivo bone bioactivity of HA nanofibers. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.