The isotropic hyperfine tensor components (a(iso)) of six neutral mono-, bi- and tricyclic dithiazole radicals are computed using the UB1LYP hybrid density functional method. They are in very good quantitative agreement with those determined experimentally by EPR spectroscopy (< 0.47 G). Thus, for the first time, a(iso) of large bi-and tricyclic hetero-radicals that contain sulfur linked to nitrogen are accurately calculated without resorting to post-Hartree-Fock techniques. As predicted, the computed hyperfine tensors show that these C-2v molecules have no magnetically equivalent atoms [1].