Temperature dependences of the e a q - spectrum and G m a x were investigated by the pulse radiolysis method over a temperature range of 25-400 o C including the supercritical condition and the e a q - formation in supercritical water (D 2 O) was confirmed. With increasing temperature, the absorption peak (λ m a x ) of e a q - shifts significantly to longer wavelength. The value of G m a x in supercritical water is considerably smaller than in liquid water at room temperature. The behavior of e a q - revealed here is helpful for an extensive understanding of water radiolysis and for the study of e a q - involving radical reactions in supercritical water.