Immunoelectrophoretic study of serum proteins in patients with various types of malignant proliferations of haemopoietic tissue was performed. It was established that myeloproliferative diseases (chronic myeloleukemia, acute leukemia) are notable for changes in alpha 2-globulins (frequent increase in the content of alpha 2-macroglobulin, haptoglobin) increase in the of beta 1 A-globulin as well as for reactive increase in the content of one or several immunoglobulins. During malignant proliferations of lymphoreticular tissue (chronic lympholeukemia, lymphosarcoma, myeloma, lymphogranulomatosis), major disturbances occur in the group of immunoglobulins, changes in which during this pathology can be of three types: reactive increase, decrease with a syndrome of antibody deficiency, paraproteinemia. The type of changes of immunoglobulins is determined by morphogenetic species of malignant cells.