Ad hoc on-demand distance vector (AODV) routing protocol is a representative ad hoc routing protocol based on an on-demand approach. In the route discovery procedure of AODV, a source broadcasts a route request (RREQ) packet to find a route to a destination. If an intermediate node has a valid route to the destination in its own route table, the intermediate node can reply to the RREQ with a route reply (RREP) packet and discard the RREQ packet. We term this mechanism as the route cache mechanism. The route cache mechanism has the merits of a short route setup time, a high route setup probability, and a small propagation range of RREQ packets. However, the route cache mechanism has the demerit of route concentration on a few mobile nodes. In this paper, we propose an enhanced AODV (EAODV) routing protocol with a selective route cache mechanism based on a source/destination pair in the route discovery procedure. By the selective route cache mechanism, EAODV can maintain the merits of the route cache mechanism and solve its demerit simultaneously. We compare the performances of the conventional AODV and EAODV in multi- hop access environment, where several mobile nodes send data packets to a fixed node such as an access point (AP), via ns-2 simulation. Simulation results show that EAODV outperforms the conventional AODV in terms of the packet delivery ratio, the average end-to-end delay, and the normalized routing overhead because EAODV can get the effect of route distribution in the route discovery procedure by the selective route cache mechanism based on a source/destination pair.