Objective: Proper management of very low weight (<1500g) infants requires specific expertise. During July and August, pediatric interns start new rotations and advance in responsibilities by postgraduate level. We test the hypothesis that low weight births in teaching hospitals exhibit increased neonatal mortality during the initial training months. Study Design: Population-based cohort of 5184 very lowweight and 15232 moderately low weight infants in California from 19 regional teaching hospitals with medical training programs. Logistic regression methods controlled for both individual covariates and temporal patterns in neonatal mortality. Result: We found no difference in neonatal mortality between very low weight infants born in teaching hospitals during July and August and those born in other months (adjusted odds ratio (AOR): 0.98, 95% confidence interval (CI), 0.78 to 1.23). Investigation of moderately low birth weight infants also indicated no increased neonatal mortality. Conclusion: Infants most likely to die in the neonatal period do not appear to be at elevated risk of neonatal mortality during July and August.