There is growing consensus that a decline in attentional control is a core aspect of cognitive aging. We used event-related potentials to examine the time course of attentional control in older and younger adults as they attempted to resolve familiarity-based and response-based interference during a working memory task. Accuracy was high for both groups but their neural response to targets and to distracters was markedly different. Young adults' early target selection was evident by 300 msec in a differentiated P3a and they responded to interference by generating a medial frontal negativity (MFN) to distracters by 450 msec that was largest when the need for interference resolution was greatest. Dipole source analyses revealed a temporal coactivation of the inferior frontal and anterior cingulate cortex in younger adults, suggesting that these regions may interact during interference resolution. Older adults did not show the early target-selective P3a effect and failed to subsequently produce the MFN in response to distracting stimuli. In fact, older adults showed a large frontal positivity in place of the MFN but, rather than serve a compensatory role, this frontal activation was associated with poorer behavioral performance. These data suggest that aging interferes with a dynamic interplay of early target selection followed by later suppression of distracter-related neural activity—a process central to the efficient control of attention.