OBJECTIVE To assess the age specific sleep time among children 1 month to 5 years of age in Shanghai, China, and to identify the related factors. METHODS A questionnaire survey was conducted among the parents of 3 266 children 1 month to 5 years of age, randomly selected in five urban districts of Shanghai in August and September of 1999 and 2000, with a response rate of 97.83%. RESULTS The total sleep time among children less than 48 months of age in Shanghai was less than that among children the same age in Western countries. The factors related to children's inadequacy of total time included parental insufficient sleep time, children's difficult temperament parental presence at sleep onset of children, and cosleeping. CONCLUSIONS The total sleep time among children at tender age in Shanghai is on the low side. The main influencing factor of insufficiency of sleep time among children is the family environmental factor, especially parental improper response to children's sleep behaviors.