Current advances in the area of wireless cellular networks, and the advent of real time services have mandated the need for an efficient network call admission controller. In this paper, we develop region-based call admission algorithms that can deal with multiple classes of prioritized real time traffic. We consider QoS metrics which arise due to mobility considerations, such as handoff and preemption call dropping probabilities. We show, using both analysis and simulations, that our call admission algorithm maintains all the QoS guarantees of the mobile users, while ensuring a high level of network utilization. Further, our call admission algorithm is computationally simple and can be efficiently implemented in modern wireless cellular architectures. The conceptual framework of characterizing call admission algorithms using admissibility sets is likely to be useful in a number of other contexts.