Two related studies are reported. Both involved the use of wrist actimetry and morning sleep logs in subjects 23-67 years of age. In the first study, 46 pairs of bed partners were monitored for 8 nights to assess the extent and concordance of their body movements, and whether the latter exhibited age and gender differences. The second study concentrated on the presence or absence of a bed partner, and included subjects who either habitually slept alone or whose usual partner was absent for at least 1 night. Men showed a significantly greater number of discrete movements during sleep than did women. Overall, 5-6% of all 30-second sleep epochs contained such movements, with about 1/3 of these movements being common (within the same epoch) to both partners. This concordance was highest in younger couples. Female bed partners reported being disturbed more often by their partner than was the case for male partners. Subjects sleeping with a partner showed a greater number of discrete movements than matched subjects who slept alone. Movements decreased during temporary absence of the usual bed partner. Couples seemed unaware of the similarity in the timing of their movements during sleep, and most reported sleeping better when their bed partner was present.