In this paper, we present a performance evaluation of a wide-area cluster system based on a firewall-enabled Globus metacomputing toolkit. In order to establish communication links beyond the firewall, we have designed and implemented a resource manager called RMF (Resource Manager beyond the Firewall) and the Nexus Proxy, which relays TCP communication links beyond the firewall. In order to extend the Globus Metacomputing Toolkit to the firewall-enabled toolkit, we have built the Nexus Proxy into the Globus toolkit. We have built a firewall-enabled Globus-based wide-area cluster system in Japan and run some benchmarks on it. In this paper, we report various performance results such as the communication bandwidth and latencies obtained as well as application performance involving a tree search problem. In a wide-area environment, the communication latency through the Nexus Proxy is approximately six times larger when compared to that of direct communications. As message size increases however, the communication overhead caused by the Nexus Proxy can be negligible. We have developed a tree search problem using MPICH-G. We used a self-scheduling algorithm, which is considered to be suitable for a distributed heterogeneous metacomputing environment since it performs dynamic load balancing with low overhead. The performance results indicate that the communication overhead caused by the Nexus Proxy is not a severe problem in metacomputing environments.