This is a prospective study, carried out over a period of seven weeks in the Parasitology-Mycology Department of the Avicenne Military Hospital in Marrakech. The objectives of my work were to -To calculate the prevalence of intestinal parasites in children. - To show the link between Giardia intestinalis infection in children and delayed height and weight gain. - To compare the performance of the two techniques, M.I.F and Ritchie, in relation to the results of direct examination. During the study period, I studied the cases of 103 children. Thirty-eight children were parasitized, with an infestation rate of 36.58%. The 6-10 age group was the most affected. Poor hygiene and the lack of awareness programmes encourage endemicity and the perpetuation of transmission. The best way to combat this misfortune is through prevention and awareness-raising.