Department of Physics, Autonomous Pest-graduate Centre, Tiruchirapalli-620 023 Department of Physics, St. Joseph's College, Tiruchirapalli-620 002 A complete vibrational analysis has been made for glyoxal-h2, -d2 and hd. A reasonable set of force constants has been obtained using the general valence force field by the Wilson's F-G matrix method. Using these values other important molecular constants such as mean amplitudes of vibration, generalised mean-square amplitudes of vibration, shrinkage constants, Coriolis coupling constants, centrifugal distortion constants and thermodynamic properties have been computed and presented. A com­parison is made between the values obtained in the present investigation and the values available in literature.