It is important to define clinical signs that can be used to identify children who have a high risk of dying from pneumonia so that these children can be given more intensive therapy. We prospectively studied 748 children in Papua New Guinea who had severe pneumonia, as defined by the World Health Organization. There was a very high mortality in children with a prolonged illness, severe roentgenogram changes, cyanosis, leukocytosis, hepatomegaly or inability to feed, and there was a trend toward a higher mortality in children with grunting or severe chest indrawing. Afebrile malnourished children had a particularly high mortality, but afebrile children had an increased mortality only if they were malnourished, and malnourished children had an increased mortality only if they were afebrile. Mortality was not increased in very young children or in children with tachypnea or tachycardia. The World Health Organization has suggested that most children with pneumonia in developing countries can be treated with penicillin but has recommended that children who are cyanotic or too sick to feed be treated with chloramphenicol because of their high risk of dying; our findings confirm that children who are cyanotic or too sick to feed have a very high risk of dying from pneumonia.