Background and Aims: Disasters constitute a major public health challenge as they can have direct and indirect consequences on the health of the populations and consequently impact health systems. After a disaster, governmental and relief organizations must identify the priorities needed for orientating actions in order to limit health consequences at short-and long-term. Health risk assessment and epidemiology can be useful tools to obtain information for such a task. Based on the comparison of responses to three disasters in three European countries, the objective was to identify and discuss common epidemiological challenges that public health institutions around Europe face in their response to disasters. Methods: The disasters chosen for comparison were the 2001 AZF factory explosion in Toulouse (France), the 2000 Enschede fireworks disaster (the Netherlands) and the 2005 London Bombings (United Kingdom). A literature review was done and exchanges between public health institutes were made. Results: The three case studies stressed the same key points: acute health risk assessment, adequate and timely environmental samples, health registering in emergency, interaction with local stake holders and victims, finding reference levels for comparison, low participation rate to epidemiological studies… Some interesting solutions could be identified as answers to these issues: steering and scientific committee, field Advice-Information Centres, Automatic Medical Registrations. Conclusions: The comparison has stressed the fact that the challenge of assessing the health situation can only be addressed by a combination of methods (health risk assessment, surveillance and surveys). Furthermore strong interaction between local stakeholders, decision makers and epidemiologists is the only way to guarantee relevant, in time, high quality and useful health impact information. Such targets can only be reached by a strong upstream preparation of post-accident management organisations. Institutes must reinforce their sharing of methodologies and their cooperation at the European level for improving post disaster epidemiological preparation.