Polarized single-crystal neutron diffraction studies of tetra-n-butylammonium tetracyanoethenide, [Bu(4)N](+)[TCNE]*(-) have been used to locate the spin distribution in [TCNE]*(-), a key component of several molecule-based magnets. This result confirms that the singly occupied orbital of [TCNE]*(-) is the pi* antibonding molecular orbital consistent with molecular orbital predictions. The results show that the spin density around the central sp(2)-carbon atoms is bent away from the midpoint of the C-C bond; it is not centered over the carbon nuclei. The spin localized on the individual sp(2)-C, sp-C, and N atoms is respectively 33%, -5%, and 13% of the total spin on the tetracyanoethenide radical. The experimental results are compared with the results from ab initio molecular orbital and density functional theory calculations. The best agreement with experiment is found at the density functional level with 29%, -4%, and 15% of the total spin on the sp(2)-C, sp-C, and N atoms. These results provide a basis to ultimately understand the ferromagnetic spin-coupling mechanism of molecule-based magnets.