We have developed a methodology that can be used to determine disjoining pressures (Pi) in both stable and unstable wetting films from the spatial and temporal profiles of dynamic wetting films. The results show that wetting films drain initially by the capillary pressure created by the changes in curvature at the air/water interface and subsequently by the disjoining pressure created by surface forces. The drainage rate of the film formed on a gold surface with a receding contact angle (0(r)) of 17 degrees decreases with film thickness due to a corresponding increase in positive Pi, resulting in the formation of a stable film. The wetting film formed on a hydrophobic gold with 0(r) = 81 degrees drains much faster due to the presence of negative Pi in the film, resulting in film rupture. Analysis of the experimental data using the Frumkin-Derjaguin isotherm suggests that short-range hydrophobic forces are responsible for film rupture and long-range hydrophobic forces accelerate film thinning. (C) 2011 Elsevier Inc. All rights reserved.