The invention relates to medicine and veterinary science and discloses a novel method for treating oncological, virulent and somatic diseases whose main target for therapeutic action is embodied in the form of DNA which freely circulates in blood plasma (and other liquid media) and originates from tumoral and mutant cells or cells infected by bacteria, fungi or protozoan and from different microorganisms which reside in the organism thereof. Said invention also relates to novel pharmaceutical compositions and to the use thereof for treating oncological diseases and infectious states provoked by bacteria, fungi and protozoa and non-infectious somatic diseases and states produced by accumulation of somatic mutations in cells of organism. Medicinal and immunological compositions, sorption and physico-chemical engineering and the method for using them in order to treat malignant tumors and other diseases are also disclosed.