Seventy-five children attending a day care center (42 girls and 33 boys, aged from 6 to 65 months) were surveyed for excretion of Giardia lamblia cysts. Cyst excretion was found in 17 (23%) of the children, 9 of whom were still positive 6 months later. Weight, height and arm skinfold thickness of each subject were obtained and compared to normal values in the Québec population; a questionnaire concerning gastrointestinal symptoms was filled out for each child. No difference in weight, height, skinfold thickness or in frequency of gastrointestinal symptoms was found when comparing cyst excretors to children with a negative stool examination. This study suggests that G. lamblia infestation has little or no nutritional impact. This should be confirmed by a larger study.