Rather recently object-oriented modeling languages, tools, and methods attract the interest of embedded (realtime) system developers. This is especially true if embedded (real-time) system software has to cooperate with interactive multimedia software, as it is more and more the case in automotive systems. It is still an open question whether and how the standard OO modeling language UML and its accompanying tools have to be adapted to the regarded application domain. To contribute useful input for this discussion we evaluated two popular CASE-tools, I-Logix Rhapsody® and Rational Rose/RT® , that implement real-time UML extensions, by developing rapid prototypes of an air condition controller.