Event-related brain dynamics of electroencephalographic (EEG) activity in a continuous compensatory tracking task (CTT) and in a continuous driving simulation were analyzed by independent component analysis (ICA) and time-frequency techniques. We showed that changes in the level of subject performance are accompanied by distinct changes in EEG spectrum of a class of bilateral posterior independent EEG components. During periods of high-error (drowsy) performance, tonic alpha band EEG power was significantly elevated, compared to that during periods of low-error (alert) performance. In addition, characteristic transient (phasic) alpha and other band increases and decreases followed critical task events, depending on current performance level. These performance-related and event-related spectral changes were consistently observed across subjects and sessions, and were remarkably similar across the two continuous sustained-attention tasks.