This work is carried out principally through the Forum on Harmful Tax Practices (the Forum), a subsidiary body of the Committee on Fiscal Affairs (the Committee). The OECD Council mandated that the Forum's work should be reviewed five years after its establishment, which occurred in 1998. The Council has also instructed the Committee to report on the results of the OECD's work in eliminating harmful tax practices in OECD member countries. This Report fulfils those mandates. Since the last report to Council in 2001, the Committee’s work has achieved significant and very positive results, as detailed in this Report. Part II of the Report focuses on the progress made in the work as it relates to OECD member countries. Part III of the Report describes the considerable progress that has been made in achieving a co-operative process with those countries and jurisdictions outside the OECD that have made commitments to transparency and effective exchange of information. Part IV of this Report describes a framework for the co-ordinated application of defensive measures to address harmful tax practices. Part V of the Report describes future work.