This paper presents a new routing algorithm for a wireless ATM LAN. The LAN combines positive aspects of connection-oriented and datagram communications schemes in its usage of the ATM VP/VC concept. In this scheme, a set of VPI trees, rooted at each node in the LAN, are preestablished. This has the effect of emulating ''connectionless'' networking which simplifies handoffs and other mobility management tasks. Given that the VPI sink trees are preestablished, there is a need for a procedure to compute and update the routes of these VPI trees with changing conditions in the LAN. Since traffic conditions are likely to change rapidly in mobile networks, we develop the Virtual Trees Routing Protocol (VTRP) to dynamically update the routing of VPI trees to handle congestion and/or topological changes in the network.