We consider the provision of Access Point buffers in WLANs. We first demonstrate that the default use of static buffers in WLANs leads to either undesirable channel underutilisation or unnecessary high delays, which motivates the use of dynamic buffer sizing. Although adaptive algorithms have been proposed for wired Internet, a number of fundamental new issues arise in WLANs which necessitates new algorithms to be designed. These new issues include the fact that channel bandwidth is time-varying, the mean service rate is dependent on the level of channel contention, and packet inter-service times vary stochastically due to the random nature of CSMA/CA operation. We propose an adaptive sizing algorithms which is demonstrated to be able to maintain high throughput efficiency whilst achieving low delay.