The 9.5 GHz electron spin resonance (e.s.r.) spectra of single crystal and powder samples of γ-irradiated taurine,, have been recorded. Overlapping spectra from three distinct radicals are present. The first of these is the species SO3−with an isotropicg-value of 2.0035 and a33S hyperfine coupling tensor with principal values 135.2, 99.2, and 97.9 G. The second radical is a π-electron species with the unpaired electron mainly on carbon and exhibiting hyperfine interaction from at least four protons, probablyand with principalg-values 2.0021, 2.0027, and 2.0034. The third radical has principalg-values 2.0024, 2.0056, and 2.0097 and principal values of the33S hyperfine tensor of 49.6, 9.1, and 1.2 G. The proposed structure for this radical is