The Unified Modeling Language (UML) has gained wide acceptance in very short time because of its variety of well-known and intuitive graphical notations. However, this comes at the price of an unprecise and incomplete semantics definition. This insufficiency concerns single UML diagram notations on their own as well as their integration. In this paper, we focus on the notation of UML-Statecharts. Starting with a precise textual syntax definition, we develop a precise structured operational semantics (SOS) for UML-Statecharts. Besides the support of interlevel transitions and in contrast to related work, our semantics definition supports characteristic UML-Statechart features like the history mechanism as well as entry and exit actions. Keywords Statecharts, UML, UML-Statecharts, Formal Semantics, Structured Operational Semantics (SOS), Labeled Transition Systems