Most parallel applications (e.g. image processing, mtdtigrid algorithms) in a Transputer-network require a lot of communication between the processing nodes. For such applications the communication system TRACOS was developed to support data transfer between random Transputers in the network. To marimize the performance of the parallel system, its dynamic internal behavior has to be analyzed. For this purpose event-driven monitoring is an appropriate technique. It reduces the dynamic behavior of the system to sequences of events. They are recor&d by a monitor system and stored as event traces. In this paper the communication system TRACOS and its performance evaluation based on monitored event traces are presented. First a synthetic workload was instrumented and monitored with the distributed hardware monitor ZM4. The results showed that the performance of TRACOS is poor for packets smaller than 4 Kbyte. Therefore, TRACOS itself was instrumented and monitored to get insight into the interactions and interdependencies of all TRACOS processes. Based on the monitoring resuhs, TRACOS could be improved which led to a performance increase of 25T0.