This second edition of the self-instructional text entitled Medical Parasitology, differs from the first edition in several ways, e.g., it has a set of learning objectives for each of the first seven chapters; it has expanded somewhat on both the graphic and descriptive materials; and a new chapter on the control and treatment of parasitic diseases has been added. The student is impressed with the necessity for studying parasitic infections in the United States on the basis of increased world travel, the influx of immigrants from areas of high parasitic disease incidence, and the general low level of understanding about their incidence and transmission within the United States. These reasons make it imperative that education in the discipline be maintained. Parasitism is explained as a biologic concept. Specific parasites of medical importance are introduced and information necessary for their recognition is presented.