Over the past 30 years, recordings of event-related potentials (ERPs) from normal individuals have played an increasingly important role in our understanding of the mechanisms of attention. This article reviews some of the recent ERP studies of attention, focusing on studies that isolate the operation of attention in specific cognitive subsystems such as perception, working memory, and response selection. Several conclusions are drawn. First, under some conditions attention modulates the initial feedforward volley of neural activity in intermediate visual processing areas. Second, these early effects can be observed for both the voluntary allocation of attention and for the automatic capture of attention following a peripheral visual transient. Third, these effects are present not only when attention is directed to a location in 2-dimensional space, but also when attention is directed to one of two spatially overlapping surfaces. Fourth, attention does not modulate sensory activity unless sensory systems are overloaded; when sensory systems are not taxed, attention may instead operate to influence memory or response processes. That is, attention operates to mitigate information overload in whichever cognitive subsystems are overloaded by a particular combination of stimuli and task.