BACKGROUND. Clinical expertise and skill of pediatric housestaff improve over the academic year, and performance varies despite supervision by faculty neonatologists. It is possible that variation in clinical expertise of housestaff affects important clinical outcomes in infants in ICUs. Objective. Our goal was to test the hypothesis that there is a decrease in morbidity and mortality in infants admitted to an NICU over the course of the academic year. DESIGN/Methods. A retrospective analysis was conducted using data on infants with birthweight 401 to 1500 g and ≥24 weeks' gestation (n = 3445) and infants with birth weights >1500 g (n = 7840) admitted to a regional NICU from January 1991 to June 2004. All infants were cared for by pediatric and neonatal housestaff supervised by neonatologists. Analysis of mortality and morbidity (intraventricular hemorrhage grades 3-4/periventricular leukomalacia, necrotizing enterocolitis ≥ Bell stage 2, and bronchopulmonary dysplasia) over time were performed by repeated measures analysis of variance and the x 2 test. Results. Mortality rate in the 401 to 1500 g cohort, as well as the >1500 g cohort did not decrease over time during the academic year and was similar between the first (July-December) and second (January-June) halves of the academic year. There were no differences noted over the academic year for any of the morbidities. Conclusions. Morbidity and mortality in infants admitted to an academic NICU did not change significantly over the academic year. These observations suggest that the quality of care of critically ill neonates is not decreased early in the academic year. opyright © 2008 by the American Academy of Pediatrics.