Norovirus infection is the most common cause of acute gastroenteritis. In immunocompetent subjects, norovirus infection is a self-limiting disease of short duration. The present report provides first evidence that norovirus can cause chronic infection in renal transplant recipients. Two patients showed persisting norovirus excretion for >7 months and 3 months, respectively. The first patient was asymptomatic after an acute episode of gastroenteritis and eliminated the virus spontaneously. The second patient developed severe symptomatic chronic infection with diffuse abdominal discomfort, fever, transient transplant dysfunction, recurrent episodes of diarrhoea, weight loss and histological signs of chronic intestinal inflammation. Norovirus elimination and relief of symptoms occurred only after reduction of immunosuppression. Thus, norovirus can evoke asymptomatic and symptomatic chronic infection in renal transplant recipients. Norovirus should therefore be considered in the differential diagnosis of both acute and chronic diarrhoea after transplantation. Reduction of immunosuppression may be indicated to allow virus elimination in symptomatic cases.