Human respiratory syncytial virus (RSV) is the major viral cause of lower respiratory tract disease in children. Infections with the virus occur as annual winter epidemics in temperate climates, placing considerable pressure on the provision of hospital beds. Most molecular epidemiological studies have, until now, focused on isolates from infants in industrialised countries. No data have been available with regard to RSV strains from northern Africa.In this report, a recent RSV outbreak in Tunisia was studied and results showed that 176 of 815 (21.6%) nasopharyngeal aspirates collected from hospitalised children were RSV-positive by immunofluorescence assay. This RSV outbreak showed a temperature-dependant pattern (P = 0.026) but no significant association with rainfall. A total of 73 RSV-positive samples were tested by two reverse-transcription-polymerase chain reaction assays (RT-PCR): RT-PCR-1, which amplifies the RNA of all RSV strains, and RT-PCR-2, which allows subgroup classification of RSV. Analysis by hybridisation assay of RT-PCR-2-amplified 1B protein gene products showed a higher prevalence of group B RSV than that of group A (82.5% vs. 17.5% among the typed strains). Knowledge of the variants is important in terms of both diagnosis and definition of a vaccine composition. J. Med. Virol. 72:683–687, 2004. © 2004 Wiley-Liss, Inc.