We propose a call admission control scheme in cellular and wireless local area networks (WLANs) integration: integrated service-based admission control with load-balancing capability (ISACL). The novel aspects of the ISACL scheme include that load transfer in the cellular/WLAN overlapping areas is allowed for the admission of originating data calls from the area with cellular access only and vertical handoff requests to the cellular network. Packet-level quality of service (QoS) constraints in the WLANs and other-cell interference in the code division multiple access (CDMA) cellular network are taken into account to derive the WLANs and cellular capacity. We model the integrated networks using a multi-dimensional Markov chain and the important performance measures are derived for effective optimization of the admission parameters. The analytical model is validated by a computer simulation. The variation of admission parameters with traffic load and the dependence of resource utilization on admission parameters are investigated. It is shown that optimal balancing of the traffic load between the cellular network and WLANs results in the maximum resource utilization. Numerical results demonstrate that substantial performance improvements can be achieved by applying the proposed ISACL scheme.