During the course of a 3-year epidemic of respiratory syncytial virus (RSV) in an Neonatal Intensive Care Unit, we examined premature neonates for the clinical features of RSV infections and the risk factors predisposing towards transmission of the disease. Seventy-nine infants with a median gestational age of 31 weeks were tested in 113 episodes of clinical deterioration for the presence of RSV antigen in nasopharyngeal secretions. Forty-seven results were positive and 66 negative. Bradycardia, which is gestational-age dependent, was the main presenting clinical symptom of an RSV infection in 75% of cases. The probability of an RSV-positive result in an episode with bradycardia, hypercapnia and fever was calculated to be 0.75. The only identifiable epidemiological risk factor was the total number of symptomatic RSV-infected infants in the ward. CONCLUSION. Bradycardia may indicate the presence of an RSV infection: the appropriate tests should be carried out and infection control reinforced immediately.