Raman spectra of crystalline sulfur samples of the mixed isotopic composition (³²S₈)_1−x(³⁴S₈)_x, where 0 ≤ x ≤ 1, have been studied. These spectra demonstrate synchronization of oscillations of S₈ molecules of the same isotopic composition which leads to “breathing” mode splitting at 211–216 cm⁻¹ (Davydov splitting). The level of splitting depends on the molecule content of the corresponding isotope and attains its maximum value of 4.5 cm⁻¹ for monoisotopic samples. If the molecules of different isotopic composition of ³²S₈ and ³⁴S₈ are adjacent, the difference in their eigen frequencies excludes the effect of splitting. For the other vibrational modes, the change in the relative content of ³²S₈ and ³⁴S₈ leads to proportional change in the intensity of the spectral bands with invariable frequencies of stretching vibrations or gradual change in the frequencies of lattice vibrations.