The science ofparasitology is particularlyrelevantto the health ofhumans and animals throughout the world. As such, it provides the core of the Rockefeller Foundation program ofbiomedical research called The Great Neglected Diseases of Mankind. While some bacterial, viral, and fungal diseases are included in this program, the parasiticdiseases caused bypro- tozoa and helminths almost uniformly fit into this category. Many ofthem infect vast numbers of people and animals (of the order of hundreds of millions), but theyare greatlyneglected bythe scientific establishmentof the modern world. The principal reason for this neglect, both scientific and financial, is the fact that these diseases are primarily problems ofthe developing world. Hence, no vaccines exist for anyofthe human parasitic diseases; for many, treatment is either nonexistent or highly toxic; and diagnosis still relies largely on the visual examination ofbiopsies, blood, and excreta. In contrast, the discovery ofa spate ofantibiotics has revolu- tionized treatment of bacterial diseases, and vaccines have been devel- opedfor manybacterial andviral diseases. Furthermore, the field ofmicro- biology, which deals largely with bacteriology and virology, has sparked the scientific revolutions ofimmunology and molecular biology. In order to examine the present status of parasitology and the reasons for its putative neglect, as well as to develop means of remedying the sit- uation, aseries ofconferences has been convened, bringing together clas- sical parasitologists and a new and complementary breed of parasite-ori- ented immunologists, biochemists, molecular biologists, and population ecologists.