In August 2002, an exceptional flood devastated a suburban area in the surroundings of Vicenza, North-east Italy. A fatal case of haemorrhagic pneumonia, which was presumptively diagnosed as leptospirosis, was observed as a consequence of the inundation. A local seroepidemiological survey was activated thereafter, with the principal aim of evaluating the risk of infection with Leptospirae in the population exposed to the flood. A 6.8% seroconversion rate was found in the population studied; however, the case previously observed remained unique, since an overt outbreak of leptospirosis did not occur.