Interrelation between acoustic emission (AE) and stress intensity factor ( K) has been examined using data generated during deformation of a series of single edge-notched tensile specimens. The experiments were carried out on nuclear and commercial grade AISI type 304 stainless steel sheet specimens of different thickness. Analyses of AE total counts ( N) versus K in log–log scale indicate N to bear the popular relationship with K as N= AK m where A and m are constants; but the magnitudes of A and m are different at low and high K regimes. Both the steels indicate higher values of m up to macroyielding than those obtained from analysis of AE data between macroyielding and the stress corresponding to K max values in the experiments. The magnitudes of m were found to be higher for the commercial grade steel than that for the nuclear grades one. In addition to the new observation of two regimes for the N= AK m relation, it was also noted that the value of m is dependent on the thickness. The variation of N with specimen thickness in the two steels appears to provide further evidence of acoustic emission from inclusion decohesion.