A unique class of conjugated compounds composed of the derivative of condensed polycyclic aromatic compound with the phenyl group and diphenyldiacetylene oligomer was synthesized by annealing of diphenyldiacetylene under elevated pressure. The effect of annealing pressure on the conductivity of the compounds was studied. The total conductivity of the compound decreased with a decrease of frequency, approaching a constant value (de conductivity : C-dc) The de conductivity of the compound increased from below 10(-15) to 10 S cm(-1) with increasing annealing pressure. The de conductivity of the oligomer was below 10(-15) S cm(-1) and that of the derivative increased from 10(-8) to 10 S cm(-1) with decreasing H/C (H/C : 0.45-0.04). The conduction of the conjugated compound was electronic. The temperature coefficient of those de conductivities was positive, with an approximately linear relation between ln(CdcT0.5) and (1/T)(0.25), where T is the temperature. The ac conductivities C-ac were proportional to temperature and frequency f and had the following equation C-ac = Tf(S), S = 0.67-0.75. These results showed that the conduction mechanism can be explained by the hopping in a manifold of states at the Fermi level.