The practice of aerating grain came into widespread use in the Southwest between 1955 and 1960. Aeration is used (1) to maintain the quality of undried grain until it can be moved through the dryer; (2) to remove harvest or dryer heat; (3) to remove small amounts of moisture (1 to 2 percent) ; and (4) to maintain the quality of grain during storage. This report is based on aeration tests conducted in a number of locations in Texas from 1954 through 1959. Most of the data were obtained from tests made in the Gulf Coast area where warm temperatures and high humidity prevail. Results from these tests provide the basis for the information and recommendations for controlling aeration fans, operating schedules, direction of airflow, and the cost of operating aeration systems given in this report.