The present invention relates to novel organic compounds comprising at least two different selections selected from the group consisting of N-phenyl carbazole, dibenzofuran, dibenzothiophene, triphenylene, aza-(N-phenyl carbazole), aza-dibenzofuran, aza-dibenzothiophene, and aza-triphenylene. The compounds are useful for organic light-emitting diodes. The compounds are also useful for charge-transport and charge-blocking layers, and as hosts in the light-emissive layer for organic light emitting devices (OLEDs).