In Expt. 1, six women were given 12 separate tests of short-duration auditory adaptation. Correlations among subjects showed that two subgroups existed, one pair differing from the others in exhibiting an interaction between stimulus strength/duration and slope of recovery. A battery of four tests is tentatively recommended that would sample the effects on different subjects of stimulus frequency, intensity, and duration, and of slope of recovery. In Expt. 2, 15 adults were given 47 tests of true auditory fatigue with pure tones. Previous data on temporary threshold shift (TTS) growth rates, equinoxious contours, recovery slopes, etc., were confirmed. An obverse factor analysis was performed, upon a correlation matrix not among tests but among subjects. A general-susceptibility grouping emerged; three individuals defined rather poorly a grouping with reduced high-frequency and increased low-frequency susceptibility; three other individuals showed recognizable specific patterns of susceptibility. Three specific tests can be shown to sample these groupings, and are recommended tentatively as an auditory fatigue battery for pure tones. Using a supplementary battery of 15 noise tests, a subgroup of three was sufficient to predict whole battery performance (r=0.81), as against a prediction (r=0.65) between any pure-tone combination versus the whole-battery noise data. Experiments 3, 4, and 5, used this information to study the prediction of susceptibility to noise-induced permanent threshold shift in man, rat, and monkey, respectively. A rather low level of success was achieved.