This prospective cohort study is one of the first to document the incidence of preventable adverse events in neonatal intensive care units (ICUs). Data on adverse events were gathered through a voluntary, anonymous incident reporting system and revealed an incidence of approximately 25 preventable adverse events per 1000 patient days—a rate similar to that in adult ICUs. The most common (and most serious) events included nosocomial infections and respiratory problems. A prior study describes the use of a voluntary safety reporting system in adult ICUs.