To determine the role of chest physiotherapy in the prevention of postextubation atelectasis in neonates intubated for greater than 24 hours, a retrospective survey compared the incidence of this complication in a newborn intensive care unit prior to and following the institution of a routine of chest physiotherapy. Eight of 23 infants extubated developed atelectasis in the "pre-physio" period, whereas only one collapse occurred in 20 infants treated with a routine of physiotherapy at extubation (P less than 0.025). Subsequently a prospective controlled trial compared the use of a routine of physiotherapy at extubation with no physiotherapy. Eight of 21 infants not receiving physiotherapy developed postextubation atelectasis and none of 21 infants receiving physiotherapy developed atelectasis (P less than 0.01). Seventy-six percent of the collapses involved the right upper lobe. A vigorous program of chest physiotherapy, including postural drainage emphasizing the positions of the right upper lobe and chest vibrations, will significantly reduce the incidence of postextubation atelectasis.