Interface kinetics often plays an important role in phase transformations. It gives rise to a deviation from local thermodynamic equilibrium at the interface between different phases and may result in various instabilities. In recent years the phase field approach to phase transformations has attracted a lot of attention and was the subject of intense investigations as it allows solving for the interface dynamics without directly tracking the interface position, which is in general a daunting problem. In this talk I will briefly review existing phase field models and will present a novel thermodynamically consistent phase field model which includes new kinetic cross-coupling terms that obey Onsager’s symmetry in the framework of linear non-equilibrium thermodynamics. I will briefly discuss the relevance of the new formulation for phenomena such as solute trapping in binary alloys and the step bunching instability in Molecular Beam Epitaxy.