Clinical and chest radiographic findings were recorded prospectively in 185 children with cough who attended an outpatient clinic in Papua New Guinea. Children were studied if they were between 8 weeks and 6 years of age; patients with wheeze, stridor, measles, or pertussis were excluded. 56 children (30%) had radiological evidence of pneumonia. The presence of either a respiratory rate greater than or equal to 50/min or chest indrawing, or of both signs, was a good indication of pneumonia, with a predictive power of 46% for a positive test and 83% for a negative test. A more complex definition of tachypnoea, as a respiratory rate greater than or equal to 40/min in children over 12 months old and greater than or equal to 50/min in infants, showed little additional diagnostic benefit.