The adsorption is studied of a fluid at a structured solid substrate by means of computer simulations on the Delft Molecular Dynamics Processor. Two types of particles are present, 2904 of one type for building a three-layer substrate and about 8500 of another type for composing the fluid. Interactions between like and unlike atoms are modeled by pair potentials of Lennard-Jones form cut off at 2.5"sigma". Simulations are performed at constant temperature and variable ratio of substrate-adsorbate to adsorbate-adsorbate attraction. On the basis of measurements of density profiles, coverages, surface tensions, and contact angles, a wetting as well as a drying phase transition have been identified. Both transitions are of first order.