The extinction coefficient of the hydrated electron (e(-))(aq) generated by pulse radiolysis is evaluated relative to the methyl viologen radical cation (MV+)-M-center dot, whose extinction coefficient at 605 nm has been carefully measured in the past. We find that the room temperature (e(-))(aq) extinction coefficients reported in the literature are underestimated by 10-20%. We obtain 6 = 22 700 M-1 cm(-1) for the 20 degrees C hydrated electron at 720 nm, assuming the (MV+)-M-center dot extinction is 13 700 M-1 cm(-1) at 605 nm. This has implications both for second-order reaction rate measurements of (e(-))(aq) and for the estimate of its integrated oscillator strength.