The present document provides guidelines for the user experience of real-time communication services. The services include person-to-person (two-way) communication and person-to-machine (one-way) communication. The present document is revised from EG 202 534 [i.11] that was restricted to person-to-person communication services. The revision adds new guidelines that have been requested by stakeholders and omits some of the previous guidelines that are no longer considered relevant. The guidelines are based on empirical data about user experience. Most of the data is obtained from scientific papers. A minority of guidelines are based on existing standardisation documents to ensure that relevant normative and informative standards material is clear amongst results available from journal articles@ conference papers@ research reports@ etc. The present document does not replace any existing standards. Most of the guidelines derived from scientific papers are specific to a particular context@ in that the original user tests were for specific tasks@ users and technical parameters and therefore the results may not be generalisable. Although the guidelines provide information about the main user experience measure(s) and technical parameter(s) of a particular test result@ it is beyond the scope of the present document to provide all of the variables concerned with each user test. However@ the origin of each empirical source of a guideline is shown and listed in the References. Those readers interested in the details of a particular guideline empirical source are also directed to a web-based system ( http://portal.etsi.org/STFs/STF_HomePages/STF354/STF354.asp) that provides this information.