To clarify the laboratory characteristics and deduce the pathogenesis of acute encephalopathy associated with multiple organ dysfunctions in Japan. We measured cytokine levels [tumor necrosis factor alpha (TNF-alpha), soluble tumor necrosis factor-receptor 1 (sTNF-R1), and interleukin-6 (IL-6)] in serum and cerebrospinal fluid (CSF) as well as general laboratory examinations in 27 patients with acute encephalopathy. Urea nitrogen (UN), creatinine (Cr), aspartate aminotransferase (AST), lactic dehydrogenase (LDH), and C-reactive protein (CRP) levels in blood, and CSF protein levels at the initial stage were significantly higher in patients with an unfavorable outcome. TNF-alpha, sTNF-R1, and IL-6 levels at the initial stage were higher in the serum than in the CSF of patients with acute encephalopathy. Serum cytokine levels correlated well with patient outcome. The high CSF protein level and the high UN, Cr, AST, LDH, and CRP levels in the blood represent the severity of vascular leakage through the blood-brain barrier and multiple organ dysfunctions, respectively, and thus suggest an unfavorable prognosis. The high serum inflammatory cytokine levels at the initial stage and the good correlation of those levels with the outcome suggest that intravascular inflammation has a significant role in vascular leakage and multiple organ dysfunctions in acute encephalopathy.