This article is chiefly a review and summary of various concepts of ego autonomy, especially Hartmann's and Rapaport's early formulations and Federn's, Weiss's, and Menninger's later contributions. The author favors Menninger's concepts, emphasizing particularly the presence of some ego energies that are independent of the id drive energies. These independent ego energies are seen especially in constructive and adaptive activities in contrast to other ego energies which are defensive and inhibitory in nature.