Background: A, severe flood occurred in Hat Yai following a torrential downpour of rain in November 2000, killing,,at least, 32 people, injuring about 1,700, and causing severe damage to property. We have assessed the effect of this disaster on. the, mental, health of the community and investigated predictors of adverse emotional responses. Method: A. cross-sectional survey using, a structured questionnaire was carried out and Thai versions of the General Health Questionnaire (GHQ) and Impact of Event Scale (IES) were administered., Data on 590 respondents residing in four areas of the city and its environs were obtained. Results: Two hundred and thirty-three (40 per cent) respondents bad a positive GHQ score suggesting a mental health problem. There were significant associations between a positive GHQ and the subjects' perception, of the severity of loss, the ability to collect, possessions, and showing a 'negative' response to the flood. High IES scores were associated with indices of the severity of loss, lower socio-economic status and minority religion. Conclusions: Natural disasters, such as floods, have a major impact on the mental health of a community, The, impact is, related to the perception of severity and loss, and is greater in lower socio-economic and minority religious sub-groups. Copyright (C) 2004 John Wiley Sons, Ltd.