Moisture meters were constructed, installed, and tested on a cotton harvester and a module builder in 1996 and 1997. Moisture contents measured during harvesting indicated a greater variation than those during moduling. Data correlated well with reference laboratory measurements with field measurements about 1% higher for the harvester and 0.5% lower for the module builder than reference lab methods. Successful operations in the field clearly indicated the utility of moisture measurements in ensuring that recommended guidelines are followed during harvesting and storage of seed cotton. Knowledge of the moisture content allows the farmer to make risk assessments to protect fiber and cottonseed quality and to ensure adequate profits.