When the first edition of this work was published 20 years ago, chemotherapy, with the exception of antisyphilitic therapy, was confined largely to tropical diseases. Since then, the discovery of the sulfonamides and the antibiotics has removed this subject from the realm of the esoteric to a place of major importance in therapeutics. As evidence of the increased scope of chemotherapy, it may be noted that the first edition of this work occupied a single volume; the present edition, when completed, will encompass four. This volume may be considered as a revision of earlier ones, since it is confined to the chemotherapy of protozoan diseases, the majority of which are tropical in origin. The diseases discussed are those due to insects (principally scabies), to helminthic infestations (amebiasis, leishmaniasis, trypanosomiasis) and to various protozoa (babesiasis, bartonellosis, toxoplasmosis, coccidiosis and trichomoniasis). The pharmacology of the agents discussed is adequately reviewed, and the