This article outlines a few of the hematologic problems that are particular to developing countries, particularly those of the tropics. Because of globalization and the increasing movement of populations, hematologists in wealthier countries must be aware of the general patterns of hematologic change in the important infectious diseases that are common in developing countries. Their manifestations are protean, and any of these diseases, malaria in particular, may present in ways that are atypical from the standard textbook descriptions. In short, the handling of hematologic disorders in developing or tropical countries is no longer confined to the physicians who work in these countries; these diseases are now part of the work of every hematologist.