To evaluate the clinical value of polymorphic marker С3435Т of MDR1 gene in the body's response to a drug in the treatment of acute brucellosis. In this article, 65 patients with acute brucellosis were examined. Genomic DNA was extracted from blood lymphocytes by standard phenol-chloroform extraction. The following primers were used for the amplification reaction, MDR1, for 5' - GAT CTG TGA ACT CTT GTT TCT A -3', MDR1, rev, 5' -GAA GAG AGA CTA ACA TTA GGC -3'. Based on general clinical, serological, immunological specific sensitization to Brucella antigen (BrAg) and tissue antigens of the liver, joint pouch (ABL - FAg), molecular-genetic (identification of personal genotype by polymorphic marker C3435T of MDR1 drug resistance gene by PCR-RFLP method) methods of research it is possible to assume, that efficiency of treatment of acute brucellosis depends on the readiness of macroorganism to the application of remedy to revealed genotype in a specific patient. Identification carriage on polymorphic marker С3435Т, serological and immunological indicators, the method of forecasting outcomes of illness, efficiency of application of medications allow us to develop a definition and giving the chance an individual approach to therapy and a choice of medical products.