In an attempt to identify physiological correlates of early (<0.2 seconds) perceptual processing abnormalities in individuals with Sensory Over-Responsivity (SOR), and to determine whether sub-types of SOR might be physiologically separable, non-invasive electrophysiological measures of auditory and somatosensory gating were obtained during a paired-stimulus paradigm in 80 adults (18-35) without current diagnoses of other psychiatric or neurological illness. These event-related potential metrics of brain function were compared to self-report rating instruments of SOR phenomena: the Sensory Profile (Brown et al., 2001, Am J Occup Ther 55:75-82) and the Sensory Gating Inventory (Hetrick & Smith, 2004, Schiz Bull, In press). Suppression (i.e., "gating") of neural activity associated with auditory event-related potential component N100 as a function of stimulus irrelevance was significantly correlated with Sensory Profile dimensions of "sensory sensitivity" and "sensory avoidance," and inversely correlated with "sensation seeking." Somatosensory component P50 exhibited a similar pattern, but the relationships did not reach significance. Sensory gating of the widely studied auditory P50, in contrast, was not correlated with any dimension of the Sensory Profile. However, suppression of this wave was correlated with the "perceptual modulation" dimension of the Sensory Gating Inventory, which generally relates to phenomena such as "being flooded by sounds" (Kisley et al., 2004, Psychophysiology, In press). Collectively, these results are consistent with the following: SOR involves increased amounts of neural processing of irrelevant sensory stimuli at the cortical level; SOR in different stimulus modalities (e.g., auditory and tactile) might be due to pathology in the individual sensory systems; more subtle differences in auditory over-responsive sub-types appears to correspond to stimulus processing abnormalities at different stages of auditory perceptual processing.