It has been reported that the mode or type of crack propagation (transgranular, intergranular, or microvoid coalescence) in 304 stainless steel could be identified by analysis of the acoustic emissions generated during crack propagation. Different crack propagation modes were produced in double cantilever beam specimens of 304 stainless steel using combinations of heat treatments and cathodic charging. The acoustic emission generated was measured, analyzed, and correlated with metallographic results. Intergranular cracking or separation was observed in three experimental conditions: (1) sensitized samples tested in air at room temperature, (2) sensitized samples which were cathodically charged prior to testing in air at room temperature, and (3) sensitized samples which were simultaneously and continuously cathodically charged while being tested at room temperature. The particular acoustic emissions generated by intergranular separations were identified by careful analysis of the acoustic emission waveforms. The amount of intergranular cracking and the acoustic emissions detected were found to be strongly dependent on the experimental test conditions. The amplitude, duration, and, hence, the energy carried in the waveforms of the emissions from intergranular separations were found to decrease dramatically when there was a constant supply of hydrogen,i.e., during continuous cathodic charging. The results are consistent with the lowering of the cohesive energy along the grain boundary; however, other mechanisms are also plausible.