The infrared and Raman spectra of H2NCN and D2NCN have been examined in the liquid state in the region of 2.5 to 35 μ. Polarization data imply a planar configuration, but the experimental data for the region beyond 12 μ are inconsistent with this. The observed product rule ratio for the symmetric N–H stretch, NH2 deformation, N–C and C≡N stretches are also inconsistent with a planar molecule. The observations do fit a nonplanar molecule with an inversion barrier described by a Manning potential. The barrier height is found to be 660 cm—1, with q0 = 0.176 Å. Every distinct feature of the infrared and Raman spectra of the liquid state for both isotopic species may be given a satisfactory assignment with this model.