There are two essential ingredients for any telecommunications system to be able to provide qualityof- service (QoS) guarantees: admission control (CAC) and service differentiation. In wireless local area networks (WLANs), it is essential to carry out these functions at the MAC level. The original version of IEEE 802.11 medium access control (MAC) protocol for WLANs does not include either function. The IEEE 802.11e draft standard includes new features to facilitate the provision of QoS, but no specific mechanisms are identified in it to make them possible. This paper introduces specific mechanisms into the relevant MAC protocol to avoid over saturating the medium (via CAC) and to decide how to assign the available resources (via service differentiation through scheduling). The main contributions of this work are a novel CAC algorithm for leaky-bucket constrained traffic streams, an original packet scheduling mechanism called DM-SCFQ, and a performance study of a WLAN including these features.