Abstract: In 1996, Hinchey et al coined the term "reversible posterior leukoencephalopathy" to describe a syndrome of headaches, confusion, and visual disturbances associated with transient, predominantly posterior lesions in the cerebral white matter on neuroimages (1).Reversible posterior leukoencephalopathy syndrome (RPLS) is often associated with an abrupt increase in blood pressure and is seen in patients with eclampsia, renal disease, and hypertensive encephalopathy.It is also seen in the patients treated with cytotoxic and immunosuppressive drugs such as cyclosporin and tacrolimus.Thus, early recognition of this condition is of paramount importance because prompt control of blood pressure or withdrawal of immunosuppressive agents will cause reversal of the syndrome.Delay in the diagnosis and treatment can result in permanent damage to affected brain tissues.A wide variety of diseases may develop RPLS and various acute neurological conditions such as stroke, cerebral venous thrombosis, encephalitis, demyelinating disorders, and collagen diseases in the brain should be distinguished from RPLS (1, 2).Malignant disease such as Hodgkin's disease or acute lymphoblastic leukemia (ALL) is a possible disease developing RPLS (1-6).Although the underlying pathophysiology of PRLS has been controversial, disturbed permeability of cerebral vessels may be one candidate.The permeability of cerebral vessels may be disturbed in many pathologic conditions including angiitis, hypertensive encephalopathy (3, 7) that may develop low density lesions in cerebral CT, prolonged T2 lesions in cerebral MRI, and hyperperfusion (8, 9) in single photon emission computed tomography (SPECT) images.Some patients with RPLS showed hypoperfusion in SPECT (10), but hyperperfusion can be also observed in these patients at least in their acute phases.