In order to determine the main clinical and laboratory manifestations associated with the infestation by an uncinaria during the first year of life, 42 children were studied from a group hospitalized between the years 1980 and 1985 in whom the main diagnosis at their time of leave from the hospital was parasitosis. Over 31 patients (74%) showed some degree of malnutrition, and severe in 24 of them (57% of the total). Clinical manifestations were mainly related to anemia (paleness, lack of air) and active intestinal bleeding (enterorrhagia, melena). Among the laboratory findings, 80% of the patients were shown to have anemia and in 24% of them, their hemoglobin levels were less than 5 g/dL, in more than half the anemia was normocytic normochromic. Also included are particularities concerning uncinariasis in the breast-feeding infant and some differences with the infection in the adult.