The immune system plays an essential part to maintaining the homeostasis of the organism. It is responsible for tolerance towards self antigens and for recognition and elimination of infectious invaders and cancer cells. Immunomodulating agents constitute a wide family of therapeutic products for the treatment and prevention of human disease and pathophysiological situations with immunological imbalances. This Forum on immunomodulators represents a selection of important examples of immunomodulating agents readily usable in human therapy. Several potential applications of cytokines as well as synthetic products are also presented.