This work presents results obtained in 90-degree peeling tests at low velocities in the case of Newtonian adhesives, when failure is cohesive. Peeling experiments are described and consider the influence of the thickness, viscosity, and surface tension of the adhesive, as well as the backing rigidity. A simple model, based on lubrication effects in thin films, is considered and compared with the measurements, when peeling is a two-dimensional phenomenon. Furthermore, a criterion for predicting the transition between the two-dimensional regime and the three-dimensional regime at higher velocities is proposed. (C) 2004 Wiley Periodicals, Inc.