Abstruct -This paper describes what automatic generation control (AGC) might be expected to do, and what may not be possible or expedient for it to do. The purposes and objectives of AGC are limited by physical elements involved in the process and, hence, the relevant characteristics of these elements are described. For reasons given in this paper, it is desired that AGC act slowly and deliberately over tens of seconds or a few minutes. From a perspective of utility operations, there is no particular economic or control purpose served by speeding up the AGC action.By this Task Force paper, the System Control Subcommittee is providing a resource to the power engineering community to help guide research into topics related to AGC.