PURPOSE: Rotavirus is one of the most important causes of nosocomial infections among children. The aim of this study is to determine the risk of nosocomial rotavirus infections and to evaluate the effectiveness of breast-feeding and probiotics in the prevention of nosocomial rotavirus infections. METHODS: This study was carried out on admitted children without diarrhea between March 1, 2003 and February 29, 2004. Three hundred ninety patients aged 4 days to 13 years during this study were available. We examined the feces of all children for rotavirus by latex agglutination on admission, during hospital, and after discharge, to see whether they developed diarrhea or not. RESULTS: Nosocomial rotavirus infections was significantly increased with children under 12 months of age(P=0.008). The monthly attack rate was great between December and March(P=0.046). Prolonged hospital stay was associated with an increased attack rate of nosocomial rotavirus infections (P=0.003). The risk of nosocomial rotavirus infections was not associated with the number of roommates and whether or not they were breast-fed or fed on probiotics. CONCLUSION: Nosocomial rotavirus infections are significantly more likely to occur in children under 12 months of age, admitted between December and March, and with prolonged hospital stays. Prompt identification and isolation of children with nosocomial rotavirus infections, even without diarrhea, may decrease rates of nosocomial rotavirus infections.