Infrared spectra of H 2S doped in Kr and Xe free-standing crystals have been measured in their S–H stretching region at 17 K. Banded structures at 2640–2600 cm −1 in Kr and at 2630–2580 cm −1 in Xe have been assigned mainly to the rotational contours of the ν 3 band of isolated H 2S in the crystals. Sharp peaks at 2575 cm −1 in Kr and 2573 cm −1 in Xe, assignable to hydrogen-bonded S–H, have also been observed. A parallel relationship between the spectral position of isolated H 2S and the polarizability of the host molecule has been observed.