New data on the wake-sleep rhythm of children aged from 2 1/2 to 4 1/2 years.

In this paper, data concerning the duration of night and nap sleep of 107 children aged from 2 1/2 to 4 1/2 years are analysed. Data were collected over a period of 9 months and showed a significant negative correlation between night and nap sleep. The reduction in the amount of nap sleep throughout the year was related to the decrease in the frequency of naps. However, its duration remained constant. The variations in the duration of the night and nap sleep were also analysed in relation to the week day and the month of the year and socio-ecological factors.