Malnutrition is a contributing cause of about half of the 10 million deaths annually worldwide, and contributes to a substantial proportion of the infectious disease morbidity among children in developing countries. Recent epidemiological and clinical evidence has shown that in most developing countries deficiencies of specific micronutrients are partly responsible for the severity of infectious disease morbidity and mortality in malnourished children. Efforts to improve micronutrient status have focused on iron, vitamin A and iodine. Supplementation with iron and vitamin A significantly reduces child mortality, while implementation of the universal salt iodization strategy reduces the incidence of iodine deficiency disorders. These strategies are considered to be among the most cost-effective health interventions in developing countries. A number of recent zinc supplementation studies in developing countries suggest that greater priority should also be given to the correction of mild to moderate zinc deficiency in children, pregnant women and lactating mothers. Some of these studies showed that zinc supplementation reduces the duration of malaria, and the severity of diarrhoea and respiratory infections (including pneumonia), and improves immunocompetence in susceptible children. The results of these studies indicate that zinc may be another specific micronutrient in which there is widespread deficiency in developing countries and that great benefits can be achieved by its supplementation.