Exposure of amorphous Fe 80B 20 alloy to two pulses of a laser beam of energy 35 Jcm −2 produces the equilibrium crystalline phase mixture α-Fe + Fe 2B at the point of impingement. Analyses of the zones adjacent to the lased area show a three-phase mixture α-Fe + Fe 3B + Fe 2B, a two-phase mixture α-Fe + Fe 3B and clusters of α-Fe in an amorphous matrix as the distance from the lased area is increased. These structures are consistent with earlier work on this alloy utilizing both continuous and isothermal annealing experiments. Although lower fluences (less than 35 J cm −2) do not seem to reveal structural transitions in transmission electron microscope analyses, field ion microscope observations show very small (less than 20 Å) clusters of α-Fe domains and an increasing number of void zones on exposure to an increased laser fluence.