Main time characteristics of sleep were studied in 9 adult dogs in experiments with 24-hr polygraphic recordings. The all-day sleep quantity (35%), circadian distribution of sleep with the maximum between 24 and 9 hours, more rapid rise of delta-sleep (DS) in the second half of day and of REM sleep in the first hours of night -- all these data suggest that the dog sleep schedule is under considerable influence of ecological factors related to time organization of activity and sleep in humans. A relatively high amount of drowsiness in dog's sleep (nearly 25%) is comparable with DS representation. REM occupies about 20% of total sleep time. Mean REM cycle lasts 30 min. The data obtained can be used as the standards of dog sleep in neurophysiological, pharmacological and behavioral studies.