The solid-liquid surface free energy gamma(SL) is an important parameter in the study of thermodynamics of the solid-liquid interface. It is a crucial parameter in the description of dendritic solidification. Xenon is a model substance for thermodynamic studies and it is a transparent model substance for metals. Xenon is used to study structure formation far from equilibrium and to model dendritic solidification of metals. gamma(SL) of xenon has been determined from equilibrium shapes of grain boundary grooves. The solid-liquid interface has been stabilized by an imposed temperature gradient. Experimental groove shapes have been fitted to a model function. Grains with various crystallographic orientations and interfaces stabilized with different gradients have been studied. gamma(SL) is found to be 9.95+/-0.68 mJ/m(2). (C) 2003 American Institute of Physics.