After having eaten dinner many customers of a restaurant in Dolo (Venice) developed gastroenteritis with diarrhoea and vomiting. Strains of non O group 1 Vibrio cholerae were isolated from rectal swabs of four customers. Epidemiological investigations revealed an association between the illness and raw oyster consumption (p = 0.008). Also, an association was found between age and illness among males (p = 0.034). As a consequence of this outbreak, a gastroenteritis surveillance programme was run for three months by health authorities in the Regione Veneto. The results indicate that, although non 0-1 V. cholerae does not account for severe pathology, it causes mild gastroenteritis and asymptomatic infections in developed countries.