Résumé : This book documents several projects which investigate adsorbate systems in or away from equilibrium and the influence of lateral interactions on their measurable properties. The kinetic lattice gas model is used to study adsorption-desorption processes as well as the diffusion of an adsorbate on a finite homogeneous one-dimensional lattice with nearest neighbor interactions. A comprehensive theory of the adsorption of CO on Ru(0001) is then developed to describe equilibrium properties as well as adsorption-desorption kinetics. Results are compared to experiment and density functional theory (DFT) calculations. This study is followed by one for O on Ru(0001) where the ramified (2x2)-O islands observed point to complex interactions between the O atoms which are modeled with a lattice gas model and DFT. This book will interest researchers in statistical mechanics, theoretical chemical physicists and their experimental colleagues.