The Raman spectra of liquid (CD3)3CH and (CD3)3CD were obtained photoelectrically together with depolarization ratios, and the infrared spectra of the corresponding gases were obtained from 3 to 35 μ. A vibrational assignment consistent with depolarization ratios and band contours has been made for the molecules on the basis ofC3vsymmetry. The spectra have been correlated with the spectra of (CH3)3CH and (CH3)3CD and modified assignments for two modes have been given for these molecules. Tentative assignments have been made for the 'inactive'A2modes (which are 'active' if the molecule has symmetryC3) to explain some of the observed frequencies around 1000 cm.−1which could not be satisfactorily assigned as summation or difference tones.