Preschool children of two villages of Kharar Taluka, Ropar district, Punjab (India) were screened for the prevalence of giardiasis. Cysts of Giardia lamblia were found in 35.1% of the stool samples and other parasites were rarely seen. The incidence of diarrhoea in association with G. lamblia positivity was 16.5% in subjects whose stool examination was positive on one or more than one occasion. No difference in the incidence of giardiasis could be seen in well nourished and undernourished children living in these endemic areas.