The  response  of  concrete  for  dynamic  loading  is  of  interest  in  a  variety  of    civilian  and  military  applications. Characterization of the  behavior  of  concrete under  dynamic  loading  is  a  prerequisite  for  the  design  and  analysis  of  these     structures. This paper present   the results of a series of experiments conducted to  investigate  the  rate  sensitivity  and  the  effectiveness  of  fiber  inclusions in  the  improvements  of  fracture  toughness  of   High  Performance  Concrete (HPC)beams. Single-edge  notched  beams  (0.5 notch  ratio)  were  loaded  in   three point  bending  over  a   wide  range  of  displacement  rates  (Do). Load-displacement  curves  show  that  their  peak  is  higher  as the  Do  increases, whereas  the   corresponding  displacement  is almost  constant. Fracture  energy, G f  also  increases  but   only  under  Do  beyond  a  threshold  value. The experimental finding of the present work addressed the positive roles of fibers (steel and polypropylene) in improving the performance of concrete under dynamic loading.