A mathematical model was developed to predict the performance of tensioned-web slot coating (TWSC), in particular, the minimum wet thickness. The model was based on the lubrication approximation for the coating solution flow and a simplified membrane theory for the moving web. The theoretical predictions compared reasonably well with available experimental data. The effects of fluid viscosity, web tension, coating speed, and wrapping angle on the performance of TWSC were evaluated. An example was presented to illustrate how die lip design could be varied to improve its performance. POLYM. ENG. SCI., 48:307-315, 2008. (c) 2007 Society of Plastics Engineers.