The electronic and the vibrational structures of TDAE(n+) (n = 0-2), where TDAE is tetrakis(dimethylamino)ethylene, have been first studied by the ab initio molecular orbital (MO) method with the 3-21G basis set. This TDAE molecule is of interest since it forms a ferromagnetic salt TDAE-C-60 but its electronic structure has never been reported. Comparison of the present vibrational analysis with the Raman spectral observation has confirmed that there is only the TDAE(+) species in the solid phase of TDAE-C-60 and TDAE-C-70.