According to a first aspect of the present invention there is provided a method of implementing a conference for a user of an IP Multimedia Subsystem (IMS). The method comprises, at a Telephony Application Server (TAS) that provides IMS multimedia supplementary services to the user, receiving a request for a conference from the user, designating a Public User Identity (PUI) of the user as an identifier for a conference service provided by the TAS that is to host the conference for the user, receiving signalling relating to a call intended for the user, and using the designated PUI to determine if the call can be connected to a conference hosted by the TAS for the user.