This report presents information on the introduction of the European Emissions Trading System as reported by the Member States (in accordance with Article 21 of the Emissions Trading Directive). It covers the period until 30 April 2005. Since the reports from Member States only cover the first four months of the first trading year the information is limited, especially concerning the real emissions and the verification procedures. However, they contain information on competent authorities, legislation and experience gained in the allocation process. Information covering the whole first year of trading - 2005 - will be reported by the Member States by 30 June 2006 and a compilation of this information will be presented by EEA by the end of 2006.