A series of 3 experiments investigated factors which could affect the morphological quality and latency of the P3 ERP component from auditory stimuli. Manipulations of attention and probability of the target tone changed P3 amplitude but typically demonstrated little effect on P3 latency. No differences for either component measure were obtained when recordings were made with the subjects' eyes open or closed. Passively ignoring the stimulus items decreased P3 amplitude and increased its latency relative to active stimulus discrimination.