Pneumonia and diarrhoeas are an important cause of toddler mortality and morbidity in developing countries. Of the 147 children admitted to the University Hospital at Kuala Lumpur in 1971 for pneumonia and diarrhoeas 50 (34%) were found to be suffering from protein-calorie malnutrition of varying degrees of severity. The malnourished children tended to come from poorer homes, and to have a larger number of siblings born in rapid succession when compared with normal weight children. Anemia was more common among the malnourished children. The interaction of infection and malnutrition and the social implications of these diseases are important. It is vital that hospitals in developing countries promote health in addition to their traditional curative role.