Acute limping in children is a common reason for consultation in pediatric emergency units. Acute leukemia is a rarely encountered disease in the orthopedic surgeon's activity. In addition, its clinical presentation is not typical and therefore is a source of possible diagnostic delay. For such reasons, there is a definite risk of undiagnosing the actual etiology of the limping episode. We report our experience with four cases of children initially seen in the pediatric emergency department for limping, as their revealing presentation of acute leukemia. The limb pain was highly variable. The radiographic work-up was always normal. Peripheral blood abnormalities were initially absent in one case and blastic cells were absent in two cases. The physician in charge should remember that paraclinical work-up normal results do not exclude a diagnosis of acute leukemia, that any drop in hematopoietic cell counts should call for a myelogram and that paraclinical exams, including the hemogram, should be repeated until a diagnosis and improvement or confirmed cure is achieved over time.