In this paper Dynamic Event Semantics, DES, is presented. DES is based on the intuition that non-stative verbs express changes. The notion of change can be made precise in at least two different, yet complementary ways. It is either an object (event, action) or a transformation of state: a state s at which a result Q does not hold is transformed into a state s' at which Q holds. An event can bring about more than one result. Each result is of a particular type that determines how it is evaluated on the execution sequences of events of a given type. The way a result is evaluated on the execution sequences of events that bring it about corresponds to a dynamic mode from Dynamic Modal Logic, which, in turn, is closely related to a type of program from Dynamic Logic. Verbs belonging to one aspectual class are characterized by determining the same types of results. Aspectual classes can therefore, at least partially, be defined in terms of types of results, or, equivalently, in terms of the dynamic modes corresponding to these types.