Vibrational relaxation in water vapor has been observed using both ultrasonic velocity dispersion and absorption. The raw data were corrected for real‐gas effects and for classical absorption. Results are compared with those of other investigators. Observed relaxation times appear much too short to be explained by a simple V‐T process, and are interpreted in terms of a V‐R transfer mechanism. Values ofkVRrange from about 1×108sec−1atm−1at 374 K to 6×108sec−1atm−1at 946 K.