Strains of Plasmodium falciparum that are resistant to chloroquine and to other widely-used synthetic antimalarial drugs have posed major difficulties in several parts of the world. Intensive efforts have been and are being made to develop new antimalarial agents that will be effective against such parasites. Several promising prospective new antimalarial agents have been identified and are now undergoing detailed clinical evaluation. The advent of one or two useful new agents should not serve as a source of renewed complacency. Parasites resistant to the latter agents may emerge and may limit their usefulness. Other new antimalarial drugs may be needed as backstops. There is and will be a continuing need to wage a strong investigative attack not only to develop new antimalarial drugs but also to develop other improved means with which to combat malaria.