ISEE-357 Introduction: During Summer 2003 much of Europe was affected by heat waves. Nationwide seasonal temperatures were the warmest on record in many countries such as France, Portugal and Italy, where an excess of mortality accompanied this unprecedented heat wave. According to the results of the Italian National Rapid Survey, carried out by the authors on behalf of the Italian Ministry of Health, Genoa was one of the cities where individuals 75 years of age or more experienced a dramatic increase in mortality. The aim of this paper is to analyse excess mortality, to investigate whether it has been a mortality displacement, to estimate the lag time between the onset of extreme climate conditions and the death, as well as to study the specific causes of death. Methods: Persons aged 75 years or more, resident and dead in Genoa during the heat wave period (16 July – 31 August 2003) were studied. Excess mortality was calculated comparing the number of deaths observed on a given day with the corresponding average value for the period 1998–2002. The relationship between mortality and climate was investigated comparing daily distributions of deaths with Humidex values.To detect the prominent causes of death during the heat wave, and to analyse all the underlying causes of death, the original death certificates of the elderly dead in the same summer period of 2003 and 2002 were examined. Results: During the examined period, 968 deaths were observed among the elderly in Genoa, compared with 633 expected on the basis of a five-years time series (SMR = 1.53, 95% C.I. 1.43–1.63). This was a significant excess mortality which was not a mortality displacement: during the months following summer (September to December) 2003 the mortality observed was not significantly different from the mortality expected on the basis of the above mentioned five-years period (SMR 1.03, 95% C.I. 0.99–1.07). The correlation between daily mortality and Humidex values was high (R2=0.501) and the lag time between the onset of extreme climate conditions and the death corresponded to a very short period (1–2 days). The prominent causes of death resulted to be cerebrovascular disesases, severe respiratory diseases, severe renal diseases, dementia; also pathologic conditions and symptoms, such as hypovolemia, hyperpyrexia, decubitus ulcers, wasting syndrome were frequent causes of death. Discussion: The relationship between mortality on one side and discomfort climatic conditions, as well as the short lag time on the other hand, give a clear Public Health message: preventive, social and health care actions have to be administered to elderly and frail people, in order to avoid excess deaths during heat waves. Particular care must be taken to the elderly affected by severe chronic diseases, in particular to those confined to bed.