Sleep after an inert capsule was compared with sleep after a hot, bedtime, milk-cereal drink (Horlicks). All-night electrophysiological recordings were made with 18 persons on 10 nights each.Restlessness during sleep at the end of the night was diminished after Horlicks in a group of 10 young adults. In an older group of eight adults, mean age 55 years, sleep after Horlicks was of longer total duration and was less broken by periods of wakefulness. In the latter group the improvement associated with Horlicks was most apparent late in the night and it increased with repeated administration.