Determining the physical location of a WLAN client includes making a request to a core network of an integrated cellular—WLAN network. Using an HLR and WLAN client identifier, the WLAN network in which the client is located is determined. A location request is then made to a MSC/SGSN servicing that WLAN network, the MSC/SGSN then forwarding the request to a gateway that interfaces the WLAN network to the core network. Alternatively, the location request is directly forwarded to the gateway. Upon receiving the request, the gateway uses a positioning procedure(s) to determine the client's physical location. This location is then returned to the core network. According to one example positioning procedure, a database containing access point physical locations is maintained. Here, a determination is made as to which access point(s) the client can communicate. The location of the access point(s), as obtained through the database, then forms a basis for the client's location.