PURPOSE: To assess how different infant positions and peak sound levels affected cerebral oxygen saturation over time. SUBJECTS: Twenty-four premature infants who were born less than 32 weeks' gestational age without congenital cardiac, neurologic, and gastrointestinal anomalies. DESIGN: Repeated-measures design with the first observation between 2 and 48 hours of life; once again between 49 and 96 hours of life; on day of life 7; and every 7 days thereafter until discharge home, transfer to another hospital, or 40 weeks postmenstrual age, whichever came first. METHODS: Continuous sound levels (decibels) were obtained and 2 infant positions were performed while measuring cerebral oxygen saturation during 40-minute observation periods. MAIN OUTCOME MEASURES: Effect of peak sound and differences in infant position on cerebral oxygen saturation. RESULTS: Peak sound levels 5 dB above the average ambient sound level did not significantly change cerebral oxygen saturation values. Differences in cerebral oxygenation were significantly less when infants were changed from a supine, head midline position to a right lateral, 15° head elevation compared with a left lateral, 0° elevation position. CONCLUSIONS: Aspects of the current neonatal intensive care unit environment do not appear to affect cerebral oxygen saturation.