A recent study has shown a 77% incidence of tracheal aspiration in children (mean age 13.4 months) who are intubated with uncuffed endotracheal tubes. To determine both the incidence of such aspiration among premature infants and whether continuous positive airway pressure (CPAP) has any preventive effect, 20 tracheally intubated neonates were evaluated for the presence of tracheal aspiration of orally placed Evan's blue dye. The overall incidence of aspiration was 80%. Eighteen of these infants were tested during both 4 cm and 6 cm H2O continuous positive airway pressure, and the incidences of aspiration were 72% and 50%, respectively, which is not a statistically significant difference (P less than .17). Ten of these 18 patients were also studied when 2 cm H2O was applied and 60% aspirated. Among all infants who aspirated, compared with those who did not, there was a small but statistically significant decrease in transcutaneous PO2 (P less than .05) as well as an increase in respiratory (P less than .001) and pulse (P less than .01) rates. It is concluded that tracheally intubated neonates frequently aspirate and that clinically useful levels of continuous positive airway pressure are not likely to prevent aspiration.