We study a new scheme for provision of priorities within the framework of a MAC protocol which is a potential candidate of the (as yet unpublished) IEEE 802.14 standard. A comprehensive simulation study, based on real traflc traces, shows that this new method provides better protection for the high priority trafic than an earlier proposed scheme. Except for physical and MAC layer overheads, the scheme exhibits comparable behaviour to that of an Ideal Multiplexer, for traces with very diverse correlation structures. The significance of using realistic (correlated) traJic streams for modelling purposes is demonstrated and discussed.