A Virtual Path(VP) concept has been proposed to simplify traffic control and resource management in future B-ISDN. Especially, significant call setup processing can be reduced when resource are reserved on VP's. However, this advantage is offset by the decrease in the statistical multiplexing gains of the networks. The focus of this paper is on how to improve bandwidth efficiency through adaptive routing when capacity is reserved on all VP's. We first examine two VP capacity reservation strategies. Eight adaptive routing algorithms, four computationally feasibleMarkov Decision Process (MDP)-based routing algorithms and four Least Loaded Routing (LLR)-based routing algorithms, are then designed and evaluated. Our simulation results show that the network blocking probability can be significantly reduced by adaptive routing.