Abstract The electrical conductivity of the condensed polynuclear aza-aromatic compounds; (1) cyananthrone, (2) indanthrone black, (3) flavanthrone, (4) indanthrone, (5) indanthrazine, (6) 5, 6-(N)-pyridino-1, 9-benzanthrone and (7) 1,9,4,10-anthradipyrimidine,—has the character of a semi-conductor. The electrical resis tivity of these compounds can be expressed as ρ=ρ0exp(Δε⁄2kT) and the mechanism of the conduction is assumed to be that of the intrinsic semi-conductor as in the cases of the condensed polynuclear aromatic compounds The value of Δε and ρ at 15° were found as; (1) 0.20 e.V., 1.2×107Ω cm., (2) 0.56 e.V., 2.5×108Ω cm., (3) 0.70 e.V., 1.4×1011Ω cm., (4) 0.63 e.V., 7.5×1014Ω cm., (5) 0.66 e.V., 1.4×1015Ω cm., (6) 3.2 e.V., 8.5×1022Ω cm. and (7) 3.21 e.V., 8.8×1024Ω cm. The values of the electrical resistivity of this group are smaller than that of related condensed polynuclear aromatic compounds.