Preterm infants in the neonatal intensive care unit (NICU) are constantly exposed to ambient noise that often exceeds recommended levels. There is a growing concern that such noise puts preterm infants at high risk for adverse health effects. This review looks at the effects of NICU noise on the cardiovascular, respiratory, auditory and nervous systems. Loud transient noise has negative short-term effects on the cardiovascular and respiratory systems of preterm infants, although direct evidence linking noise to neonatal pathology is still unclear. Further controlled trials with larger sample sizes are needed to determine the effects of more extensive exposure to NICU noise on early brain maturation and long-term developmental outcomes.