During an outbreak of haemorrhagic fever with renal syndrome (HFRS) in 1989, five children (3 girls, 2 boys, aged 6.8-16 years) with severe clinical form of the disease, were treated at the Institute of Mother and Child Health of Serbia; four of them were followed-up 22-28 months thereafter. The main clinical features were: fever, headache, myalgia, abdominal and back pains, and vomiting in all, and haemorrhagic syndrome in three; renal syndrome with severe acute renal failure in all five patients. All the patients recovered. Serological confirmation by an indirect immunofluorescence assay, enzyme immunoassay for IgM antibodies, and by plaque reduction neutralization test revealed that the infection was caused by Belgrade virus in three, and by Hantaan virus in two patients. It was not possible to differentiate these two serogroups on the basis of clinical features. This finding gave further evidence of circulation of different hantaviruses causing severe HFRS in Serbia.