X-ray and fast ion generation has been studied by femtosecond laser irradiation (52 fs, 790 nm) on metal targets (copper and iron), where hard X-ray emission takes place at power density up to 10(17) W/cm(2). X-ray intensities and kinetic energy distributions of ions are observed as a function of the power density. The ion energy distributions for each target show several peak components, which are fast ions (high-energy component in keV range), and additional low-energy component (a few hundreds of eV). Average fast ion energies show a strong dependence on the power density, and are comparable to ponderomotive potential. (C) 2002 Elsevier Science B.V All rights reserved.