The active immunization of population is a very important subset of the 21th century. The immunization is acted out with vaccines which are made of seedy bacteria or viruses, the same microorganisms which cause the variety of disorders in human organism. The immune system, after the entrance of these factors,is mobilized and produces antibodies in the same way as when a disease comes out. Antibodies destroy the seedy factors of the vaccine and the human body develops immunity. A very important factor is that the immunity is relatively permanent for a very long period, so when the individual is affected by the same factors causing the same disorder the immune system reacts more quickly for the elimination of the antigen by producing specific antibodies, and in this manner the immune system empowers and provides protection against future infections. Vaccines are also used in confrontation with various lethal diseases such as malignant tumors. In recent years, several researches have been acted out in developing new more efficient treatment options. Increased efforts have been made to apply immunomodulatory strategies in antitumor treatment. Such novel approach is the development of DNA vaccines for the destruction of malignant tumor by inducing humoral immune responces. The induction of specific immune responses directed against antigens expressed in tumor cells and displayed e.g., by MHC class I complexes can inhibit tumor growth and lead to tumor rejection. The use of different DNA delivery techniques and coadministration of adjuvants including cytokine genes may influence the pattern of specific immune responses induced. This might be the key to the future treatment of malignant tumors, increasing the life quality of patients and protecting them from relapses. Also very encouraging are the results from the clinical trials in animal models, the future studies may be focused in this way in order to render DNA vaccines safe for clinical use.