The magnetic properties of gamma irradiated single crystal cimetidine were investigated between temperatures of 123 K and 418 K and between microwave power of 0.01 mW and 150 mW by electron paramagnetic resonance. Magnetic field orientation in each of the three perpendicular axes, microwave power, and temperature dependence of the EPR spectra has led to more than one radical being produced by gamma irradiation in the host crystal. The distinctive radical was attributed to being a ring type radical; however, the other radicals could not be identified because of the superimposition. The EPR parameters of the ring type radical were determined to be: a(Hα)av = 2.42 mT, a(Nα)av = 0.62 mT, a(Hβ) av = 1.08 mT, a(Hγ)av = 0.2 mT, a(N β)av = 0.3 mT, and (g)av = 2.0030, respectively. © 2012 Elsevier B.V. All rights reserved.