We use molecular dynamics simulations to study surface-directed spinodal decomposition in unstable binary AB fluid mixtures at wetting surfaces. The thickness of the wetting layer R 1 grows with time t as a power law (R 1∼tθ). We find that hydrodynamic effects result in a crossover of the growth exponent from θ 1/3 to 1. We also present results for the layerwise correlation functions and domain length scales. © 2012 American Physical Society.