The serum vibriocidal antibody is the only recognized predictor of protection from cholera, but no seroepidemiological data have been gathered since the emergence ofVibrio cholerae 0139. We assessed the association between the vibriocidal antibody titer and protection from cholera in an endemic setting. Although a higher baseline vibriocidal titer correlated with protection fromV cholerae Ol, infection still developed in some contacts with very high titers. No association between baseline vibriocidal titer and protection fromV cholerae 0139 infection was found. Our findings suggest that the vibriocidal antibody is an incomplete predictor of protection fromV cholerae infection.