Ultrasonic absorption has been measured in H 2 S in the temperature range 300°–683°K. These data were analyzed to obtain vibrational and rotational relaxation times. The vibrational collision numbers seem to increase with temperature from 300° to 473°K and then decrease with temperature. This behavior can be explained by the v‐r theory of Shields and Burks. The rotational collision numbers compare favorably with thermal transpiration measurements.