This study determined whether the number of hours of care provided by RNs was related to mortality and complications in hospitalized children. Administrative data (1996-2001) were used to examine discharges of 3.65 million pediatric patients in 286 general and children's hospitals in California. A greater number of resource-adjusted hours of care provided by RNs was related to significantly reduced occurrences of postoperative pulmonary complications, postoperative pneumonia, and postoperative septicemia; the positive impact of increases in nurse staffing was of greater magnitude at institutions providing fewer resource-adjusted hours of RN care. There was also evidence of an impact of increases in nurse staffing on urinary tract infections, but it was statistically significant only for institutions with higher resource-adjusted hours of RN care. There was no statistically significant relationship between RN staffing and mortality. More hours of care provided by RNs was associated with improved quality of care for hospitalized pediatric patients.