Effects of lip surface topography on lubrication of radial shaft seals were studied through microscopic measurements and theoretical calculations. 3-D surface profiles of actual lip rubber compound in contact were determined with a new technique using an immersion laser-scanning microscope. Film profiles of general shaft seals in sealing and pumping conditions were measured using laser-induced fluorescent technique. The results demonstrated that the rubber surface roughness significantly affected the film thickness and the coefficient of friction. This was ascribed mainly to hydrodynamic effect caused by surface asperities, which was confirmed by a simple numerical analysis with a sinusoidal roughness.