This study aimed to observe the architecture of day sleeping after a night of work, and the characteristics of the sleep-wake cycle in nurses working in different shifts. The study was performed at the Hospital de Clínicas da Faculdade de Medicina de Ribeirão Preto, USP. The sleep-wake cycle was evaluated through the sleep diary in (n = 36) subjects, with an average age of 30 years. Of these, only five performed polysomnography measurements at the Sleep Laboratory. Subjects presented better night sleep and the polysomnography recordings identified short periods of day sleep with incomplete cycles. Subjects woke up many times, which characterizes poor sleep efficiency.43194-9