This monograph provides a systematic treatment of theabstract theory of adjoint semigroups. After presenting thebasic elementary results, the following topics are treatedin detail: The sigma (X, X )-topology, -reflexivity, theFavard class, Hille-Yosida operators, interpolation andextrapolation, weak -continuous semigroups, the codimensionof X in X, adjoint semigroups and the Radon-Nikodymproperty, tensor products of semigroups and duality, positive semigroups and multiplication semigroups.The major part of the material is reasonably self-containedand is accessible to anyone with basic...