This paper determines packet level performance measures of a MAC protocol for a wireless ATM local area network. A key characteristic of the MAC protocol is the Identi er Splitting Algorithm with Polling, a contention resolution scheme used to inform the Base Station about the bandwidth needs of a Mobile Station when no piggybacking can be used. We consider higher layer packets that are generated at the Mobile Station and investigate the in uence of the tra c characteristics of the packet arrival process on the e ciency of the protocol and on the delay that packets experience to access the shared medium.