Background: With the increasing survival rate of early preterm infants and the extensive use of invasive health care procedures, the nosocomial infection rate is on the rise in the past decade in the neonatal intensive care unit (NICU). The patients in NICU are a unique and highly vulnerable population, including preterm infants and infants requiring surgery. Nosocomial infection (NI) is associated with the majority of infectious complications of infants, resulting in morbidity and mortality. Close surveillance, accurate measurement, and promotion of full awareness of the risk factors of infection are essential to nosocomial infection control. Previous research had pointed out some factors related to the NI in other countries, and further research is still much needed to reveal the incidence of NI and further analyze the risk factors in China. Objectives: The objectives of this study were to assess incidence and epidemiologic profile of nosocomial infection in NICU of China, and to identify the main risk factors of nosocomial infections. Methods: This was a retrospective cohort with a nested case control study. All data were collected from the database of the medical records of all the patients who were admitted to the Guangzhou Women and Children’s Medical Center (N=1653) during December 2009 to May 2012.Infection rate, infection density and central line-associated bloodstream infection rate were estimated. Stepwise regression model yielded adjusted odds ratio (OR) of potential risk factors for NI. Results: The infection rate in NICU during the study period was 6.2 episodes per 100 patients (6.0-6.4 episodes per 100 patients). Infection density was 4.2 episodes per 1000 patient-days each year (95%CI=3.4-5.0 episodes per 1000 patient-days). The infection rate of ventilation-related pneumonia was 3.4 episodes per 1000 Mechanical Ventilation (MV) days. (95%CI= 3.2-3.5 episodes per MV patient-days).Central line-associated bloodstream infection rate was 5.4 episodes per 1000 central line days (95%CI= 5.1-5.6episodes per central line days). Overall, infants with gestational age >32weeks, longer duration of receipt of parenteral nutrition and longer duration of receipt of probiotics were significantly less likely to have NI (adjusted ORs= 0.35, 0.94 and 0.88, respectively). Congenital malformation, multiple birth, receipt of vein or arterial catheter, receipt of surgical operation and gastric tube feeding were significantly more likely to have NI(adjusted ORs=4.43,3.24 and 3.88, respectively). And longer duration of using prophylactic antibiotic was significantly more likely to have NI (adjusted OR=1.13). Conclusion: Our study provided information to the prevention strategies of nosocomial infections and improvement of health care service.We described the nosocomial infection rate, infection density and device-related infection rate, seasonal distribution, the type of infection and the pathogens identified to reveal the profile of nosocomial infection of NICU in Guangzhou, China.Andwe identified the association between intrinsic factors of infants and health care procedures with NI. Multicenter prospective study can be conducted in the future to investigate the specific risk factors on different birth weight or gestational age in China. / published_or_final_version / Public Health / Master / Master of Public Health