Migration has become a top priority for European Policy while international migration statistics are among the less reliable statistics within the field of socio-economic and demographic data. Already in the '70, this weakness has been pointed out by international bodies like UNECE Geneva. Within EUROSTAT, this problem has been faced continuously starting in 1990 with the production of a first report on harmonisation of international migration statistics among the 12 EU member states. Intense co-operation has been thereafter developed between all concerned international bodies in order to improve the situation including the writing of updated UN recommendations for international migration statistics. Some improvements effectively occurred but the goal of producing a set of data with sufficient reliability and minimal harmonisation and comparability is not yet achieved and policymakers express more and more their strong needs for appropriate data. Concretely this project aims to develop additional efforts parallel to the forthcoming action plan for statistics on international migration. In order to reach this objective we intend to investigate with all 25 EU MS and Acceding Countries in several directions : 1° to compare definitions and concepts related to international migration; 2° to analyse available data in order to see what the data already reveals and where are the main problems in terms of reliability and comparability; 3° to integrate data on asylum with data on flows and stocks in order to get the more reliable information on de facto international migration within each country; 4° to describe and analyse all efforts done on bilateral and international levels in order to improve the situation and to identify impact of low reliability and lack of comparability on policy implementation; 5° to propose practical recommendations on the way to improve the situation after discussion with all potential data providers and data users for migration policy develop.