Pulsed laser irradiation promotes thermal processes which can modify the microstructure of thin amorphous metallic or semiconducting films. Associated with these modifications are changes in most physical properties. In this paper, we review the variety of distinct processes which occur when either the duration or the intensity of the laser irradiation is varied. Relaxation phenomena, phase changes with emphasis on crystallization from the solid and liquid state, and ablation processes are addressed and illustrated by selected examples. © 1992.