Noroviruses (NoVs) are second only to rotaviruses (RVs) as causative agents of acute gastroenteritis (AGE) in children. The proportional role of NoVs is likely to increase after control of RV by vaccination. We investigated NoVs in children seen in Tampere University Hospital either treated as outpatients or hospitalized because of AGE before universal RV vaccination was implemented in Finland. This prospective study was conducted from September 2006 to August 2008. A total of 1,128 children