We report a nosocomial outbreak due to adenovirus in a paediatric respiratory unit serving a poor socio-economic community. Of 207 children admitted during an eight-month period, 24% were neonates; the median age of the remainder was 10 months. Thirty-two cases were found to be infected with adenovirus and of these 67% died. Nine were already infected with adenovirus when admitted. Twenty-three acquired the infection after admission, giving an incidence of nosocomial acquisition of 12% with a 91% mortality rate. All but one of the adenovirus infected children were being ventilated and had an endotracheal tube in place. Nosocomial spread was likely to have been from the hands of attendants, especially those manipulating suction catheters and endotracheal tube or ventilator connections. Risk factors for acquiring nosocomial infection were young age: all but two were < 1 year of age, and a relatively prolonged ward stay necessitated by the nature of the primary condition (pneumonia, bronchiolitis, laryngotracheo bronchitis, tetanus). The measures that were taken to control spread of the virus are described. Despite these, primary cases of adenovirus infection re-introduced the virus regularly over the study period. The genome analysis showed adenovirus types to be 7c2 and 7c.