High performance clusters are of increasing interest. In general, they consist of several heterogeneous workstations and/or PCs connected via a fast network. A large problem in this area is the efficient utilization of all available resources. Hence automated load management systems are applied. Due to the heterogeneous hardware most of standard load balancing tools can not be used because they support only homogeneous machines. In this paper the FLASH system (Flexible Agent System for Heterogeneous Cluster) is presented, which uses a mobile agent approach. Mobile agents have the capabilities to travel through a heterogeneous cluster and to fulfil jobs on the visited computation nodes. FLASH offers application programmers a framework for the creation of distributed load-balanced applications. Currently, the realization is based on Java and the agent system Voyager.