The decadic extinction coefficient of the hydrated electron is reported for the absorption maximum from room temperature to 380 degrees C. The extinction coefficient is established by relating the transient absorption of the hydrated electrons in the presence of a scavenger to the concentration of stable product produced in the same experiment. Scavengers used in this report are SF6, N2O, and methyl viologen. The room temperature value is established as 22 500 M-1 cm(-1), higher by 10-20% than values used over the last several decades. We demonstrate how previous workers arrived at a low value by incorrect choice of a radiolysis yield value. With this revision, the integrated oscillator strength. corrected by refractive index. is definitely (ca. 10%) larger than unity. This result is fully consistent with EPR and resonance Raman results Which indicate mixing of the hydrated electron wave function with solvent electronic orbitals. Oscillator strength appears to be conserved vs temperature.