Multiprocessor interconnection networks based on low dimensional mesh or torus topologies and employing wormhole switching have become increasingly popular. Two concepts that have been proposed to improve the performance of such networks are Virtual Channel Flow Control (VCFC) and adaptive routing. Some previous studies have, however, found the latter technique to yield disappointing performance under uniform traffic patterns, while in this work we show that the former technique may result in degraded performance under certain non-uniform traffic patterns. This paper studies the interaction between VCFC and adaptive routing. It is shown that each of these techniques may yield unsatisfactory performance only when used in isolation, and that through their appropriate combination uniformly improved performance can be achieved. The consistent performance improvement and the magnitude of the performance improvement in some cases offers compelling motivation for implementing a combination of VCFC and adaptive routing in future machines. 1