Recent global estimates indicate that there are 10 million deaths annually of children aged < 5 years and that 99% of these deaths occur in developing countries, with 70% caused by infections. Pneumonia is the leading cause of the infection-attributable mortality in this age-group, accounting for > 2 million of the deaths. These deaths are potentially preventable if appropriate clinical and laboratory tools are in place to facilitate early detection of the pneumonia, identification of the pathogen involved, and institution of appropriate therapy or, even better, implementation of appropriate vaccination schedules. The currently available tools for the diagnosis of acute, lower-respiratory-tract infections in children have low sensitivity and are, in any case, grossly underutilized. Consequently, there is a great shortage of the data necessary for implementing potentially effective, intervention measures. This review is of the common aetiological agents of childhood pneumonia in the tropics and of the clinical and laboratory techniques currently available for routine diagnosis. Although there are newer and more sensitive diagnostic tools, they are expensive and are not likely to be within reach of most developing countries in the tropics. There is, however, considerable scope to improve the use of the cheaper techniques, and so facilitate the development and implementation of effective control measures.