P300 event-related potentials (ERPs) from 1-, 2-, and 3-tone oddball paradigms were elicited and compared from the same subjects. In the 1-tone paradigm, only a target tone was presented, with the standard tone replaced by silence. The 2-tone paradigm was a typical oddball task, wherein the target and standard tones were presented every 2.0 s in a random order with a target-tone probability of 0.10. In the 3-tone paradigm, in addition to the infrequent target (p = 0.10) and the frequent standard (p = 0.80), infrequent nontarget tones (p = 0.10) also were presented. The subject responded with a button press only to the target stimulus in each task. The target stimulus in each paradigm elicited a P300 component with a parietal maximum distribution. No P300 amplitude differences were found among paradigms, although peak latency from the 1-tone paradigm was shorter than those from the other two tasks. Both P300 peak amplitude and latency demonstrated strong positive correlations between each pair of paradigms. The results suggest that P300 was produced by the same neural and cognitive mechanisms across tasks. The possible utility of each paradigm in clinical testing is discussed.