Slide film damping occurs when two parallel plates are in relative tangential motion. Viscous energy dissipation in the fluid between the two plates becomes a representative damping mechanism in laterally driven microdevices. In this paper, we investigate the slide film damping both theoretically and experimentally. A new physical model has been proposed for the characterization of slide film damping. Dynamic characteristics of a fluid film have been described in terms of velocity profiles, damping mechanisms, and levels of viscous energy dissipation. Simplified analytical damping formulae have been developed for practical Q estimation. The theoretical Q compares well with the experimental Q. Data reported by previous investigators are also analyzed and compared with the Q value estimated in the present study. It is concluded that our theoretical model offers simple and reasonably good quantitative prediction of Q. Possible sources of error in the theoretical Q prediction are discussed. The effects of fluid-film thickness and microstructure geometry on Q are investigated, so that the results can be used in the damping design for laterally driven microtransducers.