We report the first observation of non-equilibrium redistribution effects during laser treatment of a binary system having equilibrium segregation coefficient, k0, much greater than unity. Polycrystalline aluminium samples implanted with 30 keV Sb+ions to a dose of 1.7 × 1017ions/cm2were irradiated with single pulses (7 ns FWHM) from a Nd: glass laser operating in TEM00mode. The peak energy density (at the centre of the laser spot) varied from 2.0 to 5.7 J/cm2. A detailed liquid phase diffusion analysis, explicitly incorporating rapid melt front motion and interfacial segregation, is performed to fit the Sb depth profiles measured with a nuclear microprobe. An effective distribution coefficient k = 1 (as compared to equilibrium value of k0∼7) is obtained in agreement with the theoretical limiting value for large melt front velocities.