Summary form only given. In this paper we present a call admission control (CAC) policy for multimedia services that characterize the next generation of wireless cellular networks. The well-known CAC guard-channel policy is modified to maintain a pre-specified level of quality of services for multimedia calls. A semi-Markov decision process (SMDP) is used to represent the multi-class guard channel CAC policy with constraints on the dropping probabilities of multimedia handoff calls. The SMDP is formulated as a linear programming problem with the objectives of maximizing the system utilization and guaranteeing QoS of multiple classes of handoff calls with each class having particularly different QoS requirements. We show numerically that the multi-class guard channel policy deploying SMDP outperforms the existing upper-limit CAC policy as it improves the service quality by maximizing the bandwidth utilization while stratifying the quality of service constraint to upper bound of the handoff dropping probability.