Sleep patterns were evaluated in 100 normal men and women who did not have any complaints of a sleep disorder and who were divided into three broad age groups: 19-29, 30-49, and 50-80 years. Total laboratory recording time was held constant across all four study nights. The amount of nightly wakefulness was positively correlated with age; total wake time for the oldest age group was about two times that of the youngest group, due primarily to an increase in wake time after sleep onset, because sleep latency did not change with age. Within each of the three age groups, especially the two oldest groups, the greatest amount of wakefulness following sleep onset occurred in the final hours of the recording period. Sleep in men was characterized by a higher number of nocturnal awakenings, and in elderly men by a longer final awakening; however, other parameters of sleep efficiency did not differ considerably between the sexes.