The heat transfer properties at the melt interface of a laser surface melted and rapidly cooled material are examined. In particular, the transient values of the ratio of the temperature gradient to the freezing rate, G/R, is determined as a function of melt depth. The ratio is found to vary from infinity at the onset of solidification to zero as the surface of the material solidifies, and to be a strong function of the absorbed power density in the intermediate region of the melt layer. Systematic changes in the observed dendritic structure in several laser surface melted alloys are correlated with the calculated variations in G/R.