The alpha- and beta-phases of the thiazyl radical p-NCC6F4CNSSN center dot (1) can be selectively prepared by careful control of the sublimation conditions, with the a-phase crystallizing preferentially when the substrate temperature is maintained below -10 degrees C, whereas the beta-phase is isolated when the substrate temperature is maintained at or above ambient temperature. Differential scanning calorimatry studies reveal that the a-phase converts to the beta-phase upon warming over the range 111-117 degrees C (Delta H = +4 kJ.mol(-1)) via a melt-recrystallization process, with the beta-phase itself melting at 167-170 degrees C (Delta H-fus = 27 kJ.mol(-1)). IR and Raman spectroscopy can be used to clearly discriminate between 1 alpha and 1 beta. The alpha-phase shows a broad maximum in the magnetic susceptibility around 8 K that, coupled with a broad maximum in the heat capacity, is indicative of short-range order. Some field dependence of the susceptibility below 3 K is observed, but the lack of features in the ac susceptibility, M vs H plots, or heat capacity mitigates against long-range order in 1 alpha.