Abstract: Modeling embedded real-time systems consisting of different components with UML-RT leads to a design model using various diagrams. Sequence diagrams describe possible interactions between system components and may be annotated with specific real-time constraints. Statechart diagrams are used for describing each component's behavior. In order to be able to get a consistent model, a consistency concept for different diagram types is needed that takes into account real-time constraints. In this paper, a consistency concept for sequence diagrams and state-chart diagrams is presented which focuses on the establishment of timing constraints. Our consistency concept distinguishes between syntactical, semantic and real-time consistency and takes into account the influence of processor allocation and scheduling. Using the consistency concept we describe a method for ensuring the consistency based on worst case execution time analysis of statecharts and schedulability analysis of tasks, thereby enabling a precise answer of the question of consistency.