In this study we investigated the effects of bathing on the quality of sleep in 30 elderly people (ages 65-83 years) and in 30 young people (ages 17-22 years) in their homes. Room temperature did not vary significantly during the nights that data were acquired, ranging from 8 to 12 degrees C. After bathing and at the beginning of sleep, the mean (SE) rectal temperatures of the young and the elderly were 37.8 (0.08) and 37.5 (0.07) degrees C, respectively, and were higher by 0.7 (0.13) and 0.6 (0.07) degrees C, respectively, than when the subjects had not bathed. At the beginning of the sleep after bathing in the young subjects, skin temperature was 32.5 (0.24) and 1.5 (0.34) degrees C higher than when those subjects had not bathed. In the elderly, however, there were no significant differences in skin temperature with and without prior bathing because they used electric blankets during sleep. After bathing, the young people reported "warmth" in their hands and/or legs, while the elderly more often reported "good sleep" or "quickness of falling asleep". During the first 3 h of sleep, body movements were less frequent after bathing for both the young and the elderly subjects. The results suggest that a bath before sleep enhances the quality of sleep, particularly in the elderly.