||Two phases of 1:1 1,3,6,8-tetrakis(ehylthio)pyrene (TEPY) complex with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) have been isolated from a equi-molar mixture of TEPY and DDQ in dichloromethane by slow evaporation of the solvent. The α phase is obtained as black, branchy microcrystals and the β phase large black platelets. Both polymorphs are diamagnetic at room temperature and, in solutions, exhibit very similar electronic absorption spectra. However, their IR spectra are very different; the α phase gives broad bands while the β phase sharp peaks. The room-temperature conductivity is 0.13 and 3.0×10−6 S cm−1, respectively for the α and the β modification. The β phase crystallizes in the triclinic space group P1, with a=9.172(4), b=9.596(2), c=9.820(2)Å, α=72.60(2), β=75.89(3), γ=67.12(3)•, Z=1. The crystal structure consists of nearly planar TEPY and DDQ molecules stacking alternately along the c axis, consistent with the low conductivity of the β-phase complex.