Ultrasonic speed of sound and absorption measurements have been made in gaseous dibromomethane at 296°K, and at pressures between 0.5 and 15.0 mm Hg. Wide‐band transducers (solid dielectric microphone and driver) were used. A continuous selection of frequencies between 13 and 80 kc was used, generated as pulsed sine waves. Independent vibrational relaxation processes were found at 7.0 and 125 Mc/atmos, with corresponding relaxation times of 3.02×10−8and 0.146×10−8sec. A third relaxation process was not within the experimental range of the apparatus, and occurs below 0.1 Mc/atmos, with a relaxation time longer than 1.8×10−6sec. Seven of the nine vibrational modes have sufficient population at 296°K to contribute to the various relaxation processes. Primarily based upon the specific heat contributions of each mode, the assignments of the various modes relaxing at the different relaxation times were made. (Supported in part by the Office of Naval Research.)