This paper discusses the issue of routing packets over an IEEE 802.11 wireless ad hoc network with multiple data rates (1, 2, 5.5, and 11 Mb/s). With the characteristics of modulation schemes, the data rate of a wireless network is inversely proportional with the transmission distance. The conventional shortest path of the minimum-hops approach will be no longer suitable for the contemporary multi-rate/multi-range wireless networks (MR/sup 2/WN). We propose an efficient delay-oriented multi-rate/multi-range routing protocol (MR/sup 2/RP) for MR/sup 2/WN to maximize the channel resource utilization as well as to minimize the network end-to-end transfer delay. By analyzing the medium access delay of the IEEE 802.11 medium access control (MAC) protocol, the proposed MR/sup 2/RP is capable of predicting the end-to-end transfer delay of a routing path and find the best one. The proposed MR/sup 2/RP may choose a longer path but with less contention competitors and buffer queuing delay. Simulation results show that MR/sup 2/RP performs the load balancing and fast routing very well and its call blocking probability is obviously lower than that of conventional minimum-hops approach with fixed transmission rate.