We have carried out some experiments on KrF laser irradiation of aluminum surfaces (by using a KrF excimer laser) in air, in order to study the morphological changes induced by the laser pulses as a function of energy density and pulses number. The main parameter, of the irradiated surfaces, under investigation was the surface average roughness (SAR), which exhibits a dramatic change of behavior within three different ranges of energy, namely lower than 0.9 J/cm(2), between 0.9 and 1.6 J/cm(2), and greater than 1.6 J/cm(2). The observed morphological changes are discussed in terms of geometrical configurations leading to preferential interaction between laser pulse and irradiated surface. (C) 2002 Elsevier Science B.V. All rights reserved.