Thirty paediatric patients with acute lower respiratory tract infections (ALRI) caused by simultaneous multiple viral infections (SMV) in a 3-year interval were reviewed. Twenty patients were infected with two viruses simultaneously; nine patients with three viruses; and one patient with four viruses. The frequency of individual viruses were: adenovirus, 18 (60 per cent); respiratory syncytial virus, 7 (23 per cent); influenza virus type A, 6 (20 per cent); influenza virus type B, 15 (50 per cent); parainfluenza virus type 1, 11 (37 per cent); parainfluenza virus type 3, 13 (43 per cent). There was no difference between the clinical presentations of ALRI with SMV and those of ALRI with a single virus. In conclusion, SMV was not uncommon in children with ALRI; the clinical presentations of multiple viral infection were similar to those of single viral infection.