Exploiting the multirate capability in mobile ad hoc networks (MANETs) is more complex than in single-hop WLANs because of the rate-distance and rate-hop count tradeoffs. This paper proposes Path-centric on-demand Rate Adaptation for MANETs (PRAM) protocol. A unique feature that sets PRAM apart from most of previous studies is its path-centric approach. While others focus on finding the best data rate for each link and offering a routing path as a collection of links at their best rates, PRAM finds the best data rate for a sourcedestination pair and then, dynamically adapts it based on path lifetime and other factors. Another distinctive feature of PRAM is that it can be seamlessly incorporated with an on-demand routing protocol. Extensive performance study based on ns-2 has demonstrated that PRAM achieves as much as 71.7% higher packet delivery ratio than fixed-rate cases (6∼54Mbps) and as much as 43.2% higher than the multihop version of the wellknown ARF mechanism in a wide range of network scenarios. It is also shown that PRAM is capable of using a mixture of data rates in an adaptive manner.