Abstract. This paper describes a Java-based communication middleware, called AspectJRMI, that applies aspect-oriented programming concepts to achieve the following requirements: (1) modular implementation of its features, including those with a crosscutting behavior; (2) high degree of configurability and adaptability; (3) performance similar to conventional object-oriented communication middleware systems, such as CORBA and Java RMI. In AspectJRMI, users may explicitly select the features provided by the middleware infrastructure, according to their needs. Most of these features have a crosscutting behavior, including interceptors, oneway calls, asynchronous calls, value-result parameter passing, and collocation optimizations. In this case, they are implemented as aspects. The design of AspectJRMI follows a set of principles, called horizontal decomposition, to achieve pluggability of aspects to the core middleware implementation. This paper presents the programming interface and the implementation of AspectJRMI. It also presents experimental results of its performance.