The present study examined long-term repetition effects on human auditory event-related potentials (ERPs). ERPs were recorded from subjects performing the same multidimensional auditory selective attention task on six separate occasions spaced one week apart. The task required subjects to attend to tones that varied along the dimensions of location (L), pitch (P), and duration (D) and to detect prespecified target (L + P + D +) combinations of these attributes. Processing negativity (PN) between 100-400 ms did not change in amplitude or onset latency as a function of repeated experience with the task. In contrast, two measures of "very late" PN were reduced with practice. Specifically, the location effect measured over the 400-700-ms epoch was significant only for Weeks 1 and 2, and the separation of the L + P + D- ERP from other D- ERPs, measured over the 700-1000-ms epoch, was significantly reduced from Week 1 to Week 2. A late negative component (700-1000 ms) elicited by correctly identified targets increased between Weeks 1 and 2, consistent with subjects adopting the strategy of rehearsal of the target itself rather than the L + P + D- standard. P2 amplitude increased significantly for all standards, possibly due to decreased latency jitter in later weeks. N1 latency became significantly shorter over weeks, reflecting either increasing confidence in stimulus discrimination with repeated testing or the overlapping of an unchanging N1 with an increasing P2.