A prospective study is reported to examine the incidence of aspiration in 50 infants and children intubated with a noncuffed endotracheal tube in a multidisciplinary PICU. Aspiration was assessed by applying Evans blue dye on the tongue and searching for the dye during suctioning, in the endotracheal aspirate. Twenty-nine (58%) were medical patients and 21 (42%) surgical; ages ranged between 25 h and 4 yr (mean 18.5 months). Respiratory failure was the major indication for endotracheal intubation and mechanical ventilation in 26 (52%) of the patients, hyperventilation for increased intracranial pressure in 12 (24%), congestive heart failure in 8 (16%), and protection of airway in deeply comatose patients in 4 (8%). The patients remained intubated from 18 h to 12 days (mean 70.4 h). Evidence of aspiration was found in 8 (16%) of the patients, accompanied by changes in chest x-ray in 5 (63%) patients and a significant fall in PO2 in 3 (37%). Aspiration was not significantly affected by the presence of a nasogastric tube, level of consciousness or ventilator setting. We conclude that noncuffed endotracheal tubes of proper size that adequately seal the trachea and effectively prevent clinically significant aspiration in endotracheally intubated infants and children.