To achieve a better understanding of the diverse vulnerabilities of different social groups affected by the tsunami in December 2004 in Sri Lanka, a survey of 500 households in the Sri Lankan urban area of Galle has been conducted in cooperation with several institutes under the direction of the Institute of Environment and Human Security of the United Nations University (UNU-EHS). An important aim of the project is to analyze the determinants and effects of the migration decision at the household level to be able to support the development of appropriate prevention, assistance and resettlement policies. In this paper, we first develop a framework for analyzing the factors which have an impact on the household's decision to stay in or migrate from a tsunami-affected, risky area. By using a logistic regression analysis, this framework later provides a basis for the examination of the significance of each factor. In a second step, it is analyzed to what extent the same factors determine the probability of a household to receive financial, material, or psychological support. The results of the regression analysis indicate that especially households who have been affected by the tsunami to a great extent (e.g. by a high number of dead, missing or seriously injured household members), or households who have had bad experience with the sea already before the tsunami are more likely to migrate than others. Having relatives at a possible new place as well as having received financial and/or material support like tents or tools also both have a "pushing" impact on the household's decision to leave the area. This implies that most current support schemes encourage people to leave the high-risk areas. Factors which decrease a households' likelihood of migration are higher education, good access to information and the ownership of land and house, as well as support programs providing households with building material.