Auditory processing disorder (APD) is characterized by deficits in the auditory modality that are not due to a global processing problem or to deficiencies in the peripheral auditory system. Diagnosis of APD is time-consuming and could benefit from an objective test. Temporal processing ability is often impaired in cases of APD, which includes deficits on gap detection tasks. Previous attempts to correlate gap detection thresholds to electrophysiological responses have used the P1-N1-P2 response, mismatch negativity (MMN), and 40 Hz auditory steady-state response (ASSR), but these attempts have not been successful, especially using between-channel gap detection tasks. The current study used a modulation gap detection task and recorded the above responses to supra- and subthreshold gaps and stimuli with no gap. A significant P2 response and a later positive peak distinguished perception of a suprathreshold gap. Improvements over previous studies, the relation to auditory training, and limitations and directions for future research are discussed.