In January 2002, an outbreak of Yersinia enterocolitica O:3 infections occured on 'Asirat', an oil tanker, during its return test voyage from Split, Croatia to Trieste, Italy. Of the 120 crewmembers and workers 22 (18%) suffered from gastrointestinal symptoms. In 17 patients Y. enterocolitica O:3 was isolated from stool samples. All available food and water samples were negative and the source of infection was not determined. Probably a foodborne transmission was involved, although person to person transmission could not be excluded.