Cotton drying systems use heated air to transfer heat into the cotton and to force relative humidity very low. The accompanying increase in vapor pressure gradient moves moisture out of the cotton. Drying time for the different components of harvested cotton as a function of initial moisture content and temperature (150, 200 and 250 øF) are shown using experimental data. The test data was developed for small samples under laboratory conditions that maintained maximum exposure of the materials to constant air conditions. Typical calculations are done to show the amount of heat and moisture transfer along with the losses in typical cotton gin drying systems. The results show that the different components of harvested cotton dry at different rates and this has important implications for design and operation of seed cotton drying systems. Possible ways for modifying drying processes to compensate for different drying rates, and areas for additional research are discussed.