This paper presents a comparative analysis of alternative approaches that have been developed by IEEE, 3GPP and others for handover of PSTN and Internet sessions among multiple wireless technologies including UMTS, WiFi, WiMAX, Mobile-Fi and WPANs. It evaluates these approaches from the viewpoint of provision of QoS, Quality of Service, for seamless handover of voice, videophone, gaming, audio/video streaming and file download, and shows how QoS at the IP layer can be interworked with QoS at the wireless link layers to provide the QoS required by the user application. The method is illustrated by examples of video streaming and voice over IP.