Abstract: The IR absorption spectra of subendothelial regions of the aortic valve cusps of a patient with calcified aortic stenosis diagnosis were measured by the attenuated total reflectance (ATR) spectroscopy technique in a frequency interval of 2500–3600 cm ^–1 and analyzed in comparison to the spectra of healthy human tissues and reference spectra of a pig’s healthy bone and aortic valve. The IR absorption band structure in this spectral region was studied by means of expansion into Gaussian components. The energies of hydrogen bonds (H-bonds) involving O–H groups were estimated. It is established that, among all samples studied, the energy of H-bonds between hydroxyl groups reaches maximum in the bone tissue.