E XPERIMENTS with avian malaria have contributed a great deal to our understanding of the life cycle of the human malaria parasite. In addition, the basic studies on chemotherapy of malaria have been carried out with birds, and have resulted in the discovery of the two best known synthetic drugs, plasmochin and atebrin. No existing antimalarial drugs, however, have proven to be completely satisfactory. Moreover, the supply in this country of quinine, plasmochin and atebrin has been threatened by the blockade of the second world war. For this reason, an intensive program has been established in search for a new antimalarial drug which could be produced domestically. Consequently, avian hosts are playing an increasingly important role in malaria research in the United States. The purpose of the present paper is (i) to discuss the avian hosts of malarial parasites available for laboratory use, (X) to point out their advantages and disadvantages as tools in malaria research, (3) to provide some information concerning the supply and maintenance in the laboratory of the duck which the author believes to be the most suitable host at the present time, and (4) to list the contributions to our knowledge of the biology of Plasmodium resulting from the study of this parasite in different hosts. Canary