Technical Abstract: Aeration, the forced movement of ambient air by fan power through a grain bulk, is widely used in stored grain management programs in the United States (U.S.) to maintain favorable storage conditions for preserving grain quality. Aeration flow rates are lower than rates from grain drying, which uses very high airflow rates, and are higher than from recirculated fumigation, which uses very low airflow rates compared to aeration. Aeration is usually used to cool the grain bulk to reduce or eliminate the development of damaging organisms in the grain, while keeping humidity below levels that support storage fungi. Substantial storage losses can be caused by fungi that flourish in moist grain and by insects that can reproduce rapidly in warm grain. These losses result from interactions between the components of the stored-grain ecosystem, affected by the grain and ambient weather conditions. The role of aeration in this ecosystem is to uniformly condition the stored grain to a desirable low temperature and maintain desirable temperature and humidity conditions in the grain bulk by moving sufficient air of suitable quality through the grain. Aeration helps to equalize temperature throughout the grain bulk to prevent moisture migration and water condensation. The objective is to maintain the existing quality of bulk grain in storage. The purpose of this chapter is to guide grain managers on the concept of using aeration to preserve grain quality and manage insect populations in conventional farm and commercial grain storages.