Our objective was to examine the diagnostic yield of duodenal aspirates for Giardia in children and compare it to results of duodenal mucosal biopsies. The results of all duodenal aspirates submitted for direct parasite examinations over a 31-month period were reviewed, as were the histological results of duodenal mucosal biopsies from these patients. In all, 161 children (89 boys; age range 0.33-18 years) were included in the study. Giardia was identified in the duodenal aspirate of 5.6% (9/161) patients and on duodenal mucosal biopsies from all nine patients. In conclusion, the 5.6% diagnostic yield of duodenal aspirates for Giardia is higher than reported in a previous study of adult patients from a similar geographical region (0.7%). The detection of Giardia on duodenal mucosal biopsies from all patients with positive duodenal aspirates brings into question the utility and cost of the latter test. Duodenal aspirates for Giardia may be unnecessary if duodenal mucosal biopsies are obtained for histological examination.