The reduction of silver ions by hydrated electrons is observed at different temperatures (from 25 to 300 degreesC) at 200 atm pressure in aqueous solutions and also in supercritical water (380 degreesC at 300 atm) using nanosecond pulse radiolysis techniques. An Arrhenius plot in the range of 25-250 degreesC shows that the reaction rate constant between silver ions and hydrated electrons can be considered to be controlled by diffusion. Measurements of transient absorption spectra show that, with increasing temperature, the wavelength maxima of the absorption spectra of the silver atom and the charged dimer, Ag-2(+) are shifted to the red. The shift is more pronounced for Ag-2(+) than for Ag-0.