While aspect-oriented modeling has been recognized as a useful means of improving the modularity of software design, the de facto standard modeling language UML lacks first-class model elements representing aspects and does not provide genuine support for aspect-oriented modeling. We propose a simple extension of UML class diagrams which contains a very generic pointcut and advice language and facilitates to model with aspects. Using this approach, we achieve a better separation of concerns as well as more redundancy reduction in UML class diagrams and make them thus more readable and better maintainable.