Lactoferrin, an evolutionarily old protein of the transferrin family, is among the proteins constituting the system of innate immunity; its action, however, also extends to the regulation of acquired immunity and other immunological phenomena. The actions of LF, confirmed in numerous in vitro and in vivo models, include participation in iron homeostasis, immunoregulatory properties, anti-inflammatory, anti-tumor, and analgesic actions, regulation of bone metabolism, participation in embryonic development, reproductive functions, and others. LF plays an important role in the normal development of a newborn. The anti-tumor properties of LF were discovered about a decade ago and have been confirmed in many laboratory, preclinical, and clinical studies. The immunomodulatory properties of LF play a major role in its anti-tumor actions. Such actions of LF appeared particularly effective in cancer patients with impaired immunity. The growth of tumors is facilitated by low expressions of MHC and co-stimulatory antigens on tumor cells and the induction of suppressor cells and other inhibitory products by tumors. Enhancement of an anti-tumor immunological response may, therefore, restrict tumor growth. Studies showed that LF elevates the number and increases the activity of T and B lymphocytes and NK cells, stimulates the release of a number of cytokines (IL-1, -6, -8, -18, IFN-gamma, TNF alpha), increases phagocytic activity and cytotoxicity of monocytes/macrophages, accelerates the maturation of T and B cells, and elevates the expression of several types of cellular receptors, such as CD4, zeta chain of the CD3 complex, LFA-1, CD11, ICAM-1, and selectin P. Apart from its immunomodulatory properties, LF exhibits direct anti-tumor actions, such as lytic, pro-apoptotic, anti-proliferative, anti-angiogenic, anti-oxidant activity and the chelation of iron ions. LF also possesses chemo-preventive properties, regulates the activity of phase I and II enzymes participating in the activation and detoxification of carcinogens, and regulates the composition of the intestinal microflora. In this way it prevents the generation of tumors and their development at early stages of carcinogenesis.