[en] Advances in radio astronomy and quantum electronics have led to research on submillimeter spectra for polyatomic molecules, particularly ones of symmetrical top type, and there is now realistic scope for determining the exact structure on the basis of rotational and centrifugal parameter of any order. A direct impetus to this study was provided by the observation of submillimeter lasing by Cd₃Cl, which occurs on transitions in the excited vibrational states v₂ and v₅, but a quantitative description of the lasing is much assisted by an exact calculation on the ground-state rotational spectum. Rotation and centrifugal constants are given which provide a reliable basis for accurate calculation of the submillimeter rotational spectrum of CD₃Cl and provide valuable information on the geometry and force field