A call admission control algorithm must try to admit as many calls as possible provided their quality of service (QoS) requirements can be met without violating those of previously admitted calls. In this paper, we propose a simple and effective call admission control algorithm and its associated resource allocation mechanism together will be referred to as the flexible call admission control, for recently proposed multi-pattern (MP) wireless local area networks (WLANs). The proposed flexible call admission control effectively takes the advantages of flexible pattern assignment in MP WLANs and the rate-adaptive feature of multimedia services to support multiple classes of traffic with diverse QoS requirements and priority levels. With the use of an innovative performance estimation mechanism, the proposed flexible call admission control and resource allocation algorithm has considerably lower complexity than that of the existing schemes. Simulation results have demonstrated that the use of MP FAC provides much higher system throughput and lower call blocking probability. It should be emphasized that the proposed FAC, although designed for MP WLANs, also works well with existing standard WLANs.