The 40-items of sleep-wake pattern (SWP) questionnaire were selected among the short statements of a former 200 items list using statistical procedures (Putilov, 1990). The analysis of the multivariate structure of the questionnaire revealed 3 scales and 2 subscales which can be labelled as levels of morning (M) and evening wakefulness (E), quality of sleep (S), capacities to be awake (w) and to fall asleep at any time (f). High positive scores indicate lateness in the morning or evening on М- and E-scales, good sleep on S-scale and high capacities to change time of sleep or wakefulness on f- and w-subscales. The age- and sexrelated variability of the questionnaire scores was studied in a town population (2000 males and 2126 females aged 9 to 79 years). All scale and subscale scores are near zero in the thirties, higher in younger and lower in older age, and in all age groups females show lower adaptability of sleep-wake cycle (higher М- and lower E-, S- w-, /-scores).