Neural correlates of age-related declines in prospective memory were studied by using event-related brain potentials (ERPs) in a task in which individuals formed and later realized simple intentions. The behavioral data revealed that prospective responding was less accurate and slower in older than in younger adults. The electrophysiological data revealed age-related differences in the amplitude of modulations of the ERPs associated with the encoding of intentions, the detection of cues, and disengagement from the ongoing activity. These findings support the hypothesis that age-related declines in prospective memory result from a reduction in the efficiency with which older adults encode intentions and detect cues.