An outbreak of 12 cholera cases, caused by Vibrio cholerae eltor inaba, occurred in Hong Kong during a three week period in June-July 1994. Only adults of both sexes were affected. Epidemiological investigations showed linkage in all cases with consumption of seafood, including shellfish, mantis shrimps and crabs. Microbiological findings demonstrated that contaminated seawater in fish tanks used for keeping alive these seafoods is the most likely vehicle of transmission. Aggressive control measures, promptly instituted, included prohibition of use of contaminated typhoon shelter water in fish tanks, use of seawater with E. coli counts below 610 organisms/100 ml, and the banning of unlicensed food sampans in typhoon shelters. These measures, coupled with public announcements and an active health education campaign on food safety and personal hygiene, abruptly terminated the outbreak. Places which practise the use of seawater, from probable contaminated sources, to keep alive their seafood for human consumption should be alerted to the possibility of transmission of Vibrio cholerae through this route.