Tunable second harmonic radiation has been generated on a gold surface by means of a dye laser system capable of emitting pulses of 450 fs and 4.5 ps duration. The intensity of harmonic radiation was maximum along the direction of the reflected incident laser beam, when the polarization direction of the incoming radiation was vertical to the target surface (ppolarization). The efficiency for second harmonic generation was found to depend strongly on the pulse duration of the laser beam. The observed change of the harmonic generation efficiency as a function of the angle of incidence and the pulse duration of the laser beam suggests that, due to coherence effects, the actual overlapping spatial dimension of the interaction region between the laser pulse and the electron gas of the metallic surface plays an important role. ©1995 American Institute of Physics.