Purpose : This study was conducted to investigate the incidence and clinical manifestations of rotaviral infections in the neonatal intensive care unit (NICU). We also investigated whether neonates referred from other hospitals cause outbreaks of rotaviral infections in the NICU.Methods : Neonates diagnosed with rotaviral infections in the NICU at Korea University Ansan Hospital between January 2002 and December 2006 were evaluated retrospectively. Results : Of 1,501 neonates admitted to the NICU, the number of rotaviral infections was 94 (6.3%) and the prevalence was 4.9 cases per 1,000-hospital days. Of 223 neonates referred from other hospitals to our NICU, 24 (10.8%) were confirmed to have rotaviral infections at the time of referral. Common symptoms of rotaviral infections were jaundice diarrhea or loose stools, vomiting, fever, apnea, irritability, seizures, and moaning sounds. Necrotizing enterocolitis of stage II or more was diagnosed in 3 premature neonates, accounting for 3.2% of total infected neonates and 6.8% of premature infected patients. There were no statistically significant differences in the prevalence of symptoms between term and preterm neonates, except for jaundice that is more frequent in premature infants. In time series analysis, the admission of neonates who were born at other hospitals and diagnosed with rotaviral infections were associated 1 month later by increased cases of neonates with rotaviral infections who were born at our hospital, whereas new cases of rotaviral infections among inborn neonates were decreased 2 and 4 months later (P<0.05). Conclusion : Rotaviral infections in NICU were not rare and showed vague symptoms. Three cases (3.2%) were diagnosed with stage II or more necrotizing enterocolitis. The referred neonates with rotaviral infections may induce outbreaks in the NICU, therefore awareness and strict surveillance for rotaviral infections should be performed at the time of referral.