We have studied the incidence of enterotoxigenic Escherichia coli (ETEC) strains isolated from infants with and without diarrheal diseases in Vanuatu, South Pacific. Over a period of 5 months we have isolated enterotoxigenic E. coli strains from 29 (26.6%) of 109 children with acute diarrhea and from 13 (21.6%) of 60 children of the control group. In the group with diarrhea, 7 (6.4%) strains released heat-labile toxin, 7 (6.4%) released heat-stable toxin, and 15 (13.7%) produced both heat-labile and heat-stable toxin. In the control group, oiily one strain (1.6%) produced heat-stable toxin, 12 (20%) produced heat-labile toxin, and none produced both. Association of strains releasing heat-stable toxin or both heat-labile and heat-stable toxin with diarrhea was highly significant as shown by statistical analysis. The serogroups and colonization factors CFA/I and CFA/Il are presented.