The clinical and laboratory features of persistent diarrhea were investigated in 83 children under three years of age who were treated in the Gastroenterology Division of the Institute for the Protection of Children's Health, Hanoi from August 1988 to August 1989. The number of cases of diarrhea was highest in the children aged 4-5 months. The mean age of the children studied was 6.6 +/- 3.4 months. The ratio of males to females was 2.6 and mean age of first episode of diarrhea was 4.3 +/- 3.4 months; persistent diarrhea was more common in children under six months of age than in older children. Persistent diarrhea occurred in the first diarrheal episode in 66.5% of cases. Recent nonenteric infections were found in 30% of the study group. Of the 83 children studied, 36% had stool specimens positive for enteric pathogens; 24% had enterotoxigenic Escherichia coli isolated, 8% had enteropathogenic E. coli, 5% rotavirus, 6% Candida, and 4% Giardia lamblia. The duration of diarrhea was longer in children who received antibiotics than in those who did not (p < 0.01).