Abstract In this paper, an agent based WLAN/cellular network integrated service model and relevant authentication scheme is proposed. The service model, or solution, does not require cumbersome peer-to-peer roaming agreements to provide seamless user roaming between WLAN hotspots and cellular networks, which are operated by independent wireless network service providers. Security analysis and overhead evaluation are given to demonstrate that the proposed service model and the supporting schemes are secure and effective. Keywords - authentiction; security; agent; WLAN/cellular integrated service