Hemolytic uremic syndrome (HUS) in children is classically associated with diarrheas related to the production of a shiga-toxin. HUS occurs among oncologic patients, in relation with the cancer itself, or as a complication of the cytostatic treatment. The physician should be familiar with the triad of HUS (microangiopathic hemolytic anemia, thrombocytopenia and renal failure) and search actively for this pathology in oncologic patient. The treatment is essentially empirical. It includes plasma exchanges, control of blood pressure, hydro-electrolytic balance control with dialysis, if necessary. Blood transfusion should be avoided. Potential mortal complications associated with HUS can be prevented by a rapid diagnosis and a prompt initiation of adequate therapy.