Polysaccharides constitute a structurally diverse class of biological macromolecules with a wide range of physicochemical properties, which are the basis for the different applications in the broad field of pharmacy and medicine. Besides the classical applications of these biopolymers in industry and pharmaceutical practice, the relatively new field of the physiologically active polymers will be discussed. Some examples will be given for the so-called immune-modulating antitumor polysaccharides which have been shown to be prominent candidates for an adjuvant tumor therapy.