Reversible posterior leukoencephalopathy syndrome is a clinical-radiological phenomenon associated with headache, vomiting, lethargy, visual disturbances and seizures, concomitant with radiological abnormalities predominantly within posterior cerebral white matter due to cerebral edema. There are multiple triggers as acute hypertension, cancer, hematological disease, renal pathology, red cells transfusions and different drugs. We present two patients with reversible posterior leukoencephalopathy under treatment for acute lymphoblastic leukemia because of the probable association with vinca alkaloids.