A variety of transient radicals, RnM·, add to di-tert-butylsulfur diimide to give a new class of nitrogen-centered radicals, N-aminothiyl-N-alkylamino radicals, Me3CṄSN(CMe3)MRn. The EPR parameters of these radicals indicate that the unpaired electron is located principally in the Nα 2pz orbital and that the α-tert-butyl group, the two nitrogens, and the sulfur lie in, or close to, the nodal plane of this orbital. These radicals decay with first-order kinetics, and some of them are very persistent. Radical addition to di-tert-butylcarbodiimide appears to be a less facile process, since only CF3O· gave a simple adduct, Me3CN=C(OCF3)ṄCMe3. This 1,3-diazaallyl radical decays with second-order kinetics; log (k/M-1 s-1) = (7 ± 1) - (2.5 ± 1.2)/θ, where θ = 2.3RT kcal/mol. Trimethysilyl radicals add to di-tert-butylcarbodiimide (and other carbodiimides), but only the extremely persistent (Me3Si)2ĊN(SiMe3)2 radical can be observed.