A visible probe laser (632. 8 nm) was used to directly observe motion of the melt front in silicon-on-sapphire during pulsed laser annealing. The average penetration and regrowth velocities have been determined to be 13 and 6. 5 m/sec. respectively. These values are in agreement with recent conductivity measurements and heat flow calculations. In addition, the data demonstrate that the high-reflectivity phase can penetrate at least 0. 5 mu m (Si thickness) and requires a significant amount of time to do so. These results are further evidence that the high-reflectivity phase is molten silicon. 6 refs.