This contribution describes surface-initiated atom transfer radical polymerization (ATRP) to produce dense polymer nanolayers. We will outline a kinetics model for surface-initiated ATRP, and apply this model to describe the polymerization kinetics of styrene at 60 °C using the CuBr/PMDETA catalyst/ligand system. Previously, we showed that surface-initiated ATRP of styrene at low temperature avoids problems with thermal self-polymerization and side reactions, thereby retaining control. Here, a wide range of monomer concentration was studied in order to determine the reaction order with respect to the monomer concentration. In anisole, the polymerization rate was first order with respect to monomer concentration at low monomer concentration and became zero order for higher monomer concentrations. This rate order transition will be discussed in the context of the model development. We will conclude the presentation with a discussion of how surface-initiated ATRP is being used in our lab to prepare specialized polymer nanolayers for gas separations.