Abstract: A combination of high-resolution agarose gel protein electrophoresis, refractometric analysis, and infrared spectroscopy was applied to investigate the blood serum in patients with multiple myeloma (MM). Analysis of the FTIR spectra of the serum obtained from MM patients and healthy donors revealed a decreased amount of α-helixes and increased content of β-sheets in serum proteins from MM patients compared to healthy donors. These findings suggest an interaction between serum proteins and stabilization of the resulting complexes, accompanied by the formation of associated β-sheets.