New onset of childhood acute leukemia may present to the emergency department in a variety of ways. This report describes the case of a 3-year-old boy who refused to walk and had minimal physical findings, normal X-rays, and nearly normal lab screening results. His white blood cell count differential led to the diagnosis of acute leukemia. The presentation and evaluation of acute leukemia in children is reviewed. Emergency physicians must be prepared to rule out malignancy in the child who refuses to walk when other more common causes, such as infection and trauma, seem unlikely.