We aimed to evaluate rotavirus morbidity and describe rotavirus epidemiology in hospitalized children in Norway to provide information before the introduction of new rotavirus vaccines. We retrospectively reviewed 14,973 gastroenteritis hospitalizations in children aged <5 y for the period 1995 to 2004, and prospectively surveyed for rotavirus in 311 children aged <5 y admitted with diarrhoea to 3 hospitals in 2006-2008. The proportion of rotavirus among all gastroenteritis hospitalizations was estimated at 14.5% from the retrospective data and at 62.9% in the prospective data. The annual incidence of rotavirus hospitalizations is estimated to be 3 per 1000 children <5 y of age, corresponding to approximately 900 (range 735-1092) hospitalizations each year. Children aged 6-23 months accounted for 61% of all confirmed rotavirus cases, and average duration of hospital stay for rotavirus cases was 1.3 days. We observed a predominance of rotavirus infections from March through May, similar to the seasonality of diarrhoea-associated hospitalizations with viral and unspecified aetiology. No rotavirus-associated deaths were reported. It is estimated that two thirds of all gastroenteritis hospitalizations in children <5 y of age may be attributable to rotavirus in Norway. Continued surveillance and further studies are needed to assess the full burden of rotavirus disease and its economic impact in Norway.