This Study provides support to the European Commission in its revision of the 2002 guidelines on market analysis and the assessment of significant market power for electronic communications networks and services ("2002 SMP Guidelines"). The main issue explored both from an economic and a legal perspective is the concept of joint SMP of telecoms operators for the purpose of ex ante regulation in the electronic communications sector. The Study also analyses developments in the concept of market definition and the finding of individual SMP as well as implications of the proposed European Electronic Communications Code for the market analysis process. In addition, it covers all the sections of the 2002 SMP Guidelines. The analysis is based on a review of competition case-law, detailed case studies of relevant market analyses conducted by NRAs, the analysis of economic evidence and the results of an interactive workshop with BEREC and NRAs, in which various hypothetical market scenarios were considered. The conclusions of the Study regarding joint SMP are based on general competition law principles, drawing in particular from the ECJ's findings in Airtours and Impala. It takes into account particularities of the electronic communications sector and the extensive experience of market regulation by NRAs in order to suggest the main steps that could be taken by NRAs when assessing whether a market is characterised by joint SMP, and the evidence that could be presented, respectively, in the case there is no pre-existing regulation and where such regulation exists and might affect wholesale and retail outcomes.