The IR spectrum of isoflurane dissolved in liquid Kr, and Xe, and Raman spectrum of pure liquid are registered and analyzed. Fundamental bands are assigned using “anharm” option of ab initio calculations. Estimations based on calculated thermodynamic and spectroscopic parameters confirm experimentally found temperature effect of noticeable redistribution of intensity of selected pair of bands ascribed to the most populated two rotamers. Concentrations of two rotamers become comparable at T∼295 K.