[en] International Atomic Energy Agency (IAEA) carried out the Co-ordinated Research Program (CRP) ON ^Validation of Accident and Safety Analysis Methodology'' in the period between 1995 and 1998. Three areas of interest identified by the participants referred to the pressurised water reactors of Western and Eastern type (PWR and WWER type). The specific areas of attention were: system behaviour of the primary and secondary loops (PS area), the containment response (CO area) and the severe accidents (SA area). During the CRP it became clear that the technology advancements, the available tools (i.e. codes) and the experimental databases in the above areas are quite different. At the conclusion of the CRP, all objectives of the program have been reached. This paper presents the summary of the regional co-operation in this framework. The CRP activities focused on the codes and expertise available at the participating organisations. This overview therefore summarises their experience related to the state-of-the-art in the field of computational accident analysis. In addition, the paper proposes the recommendations for future activities related to the code usage, the user effects and code development. In pursuing of these goals special attention is given to the importance of the international co-operation. (author)