Since the first version of the IEEE 802.11, the standard committee has included a set of transmission rates aiming to accommodate the wide variety of requirements of end-user devices and channel operating conditions. Traditionally, the sender increases the data transmission rate upon receiving various consecutive acknowledgement packets while the data transmission rate is decreased on the absence of acknowledgement packets. This error-control procedure assumes that the channel operating conditions are the main source of transmission errors and losses. However, under medium or high load conditions, transmission impairments are mainly due to channel access conflicts: collisions. Under these load conditions, reducing the data transmission based exclusively on the absence of feedback not only proves ineffective, but it actually degrades the overall network performance. In this paper, we describe a novel rate adaptation mechanism capable of mitigating the effect of collisions using the information imbedded in the received packets. Simulation results show that our proposal limits the use of the data transmission adaptation mechanism which in turn results on a significant increase of the aggregated throughput.