Cotton gin drying systems were mathematically modeled using calculations based on laboratory data showing drying rates for small samples. The model was used to predict expected moisture transfer rates for different components of machine-stripped cotton in typical cotton gin drying systems. The calculated results were compared with actual results for two types of gin drying systems. The source of apparent rewetting that has been noted in seed cotton downstream of gin drying systems was examined using vapor pressure relationships. Possible ways for modifying drying processes to compensate for component drying rates, and to maintain the drying gradient are suggested. The results show that some rethinking of cotton gin drying processes is in order and additional research is needed. Fundamental data showing vapor pressure for cotton in terms of temperature and moisture level is needed so that it can be integrated with vapor pressure and temperature data for air to describe the interactions through the entire drying system and allow design of ways to compensate for imbalances originating from the drying process.