Nanofibers of poly (lactic acid) (PLA) and poly (caprolactone) (PCL) with different amounts of nanohydroxyapatite (nHA) were produced by electrospinning, changing both the applied voltage and collector's rotation. Characterization of the nanofibers by scanning and transmission electron microscopy (SEM. TEM), wide angle X-rays diffraction (WAXD), infrared (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMTA) showed that the PLA/nHA fibers had larger diameters, lower crystallinities, lower degradation temperatures and higher elastic modulus than the PCL/nHA nanofibers. The crystalline phases of the PLA/nHA fibers were a mixture of alpha and alpha' phases, while the crystalline phase of the PCL/nHA samples was mainly alpha phase. In both set of mats, the highest amount of viable cells with early osteogenic activity after 7 days was obtained with the mats with the highest amount of nHA (5 wt%), the lowest amount of crystallinity and the highest elastic modulus. (C) 2012 Elsevier Ltd. All rights reserved.