(Chemical Equation Presented) In this paper we present the synthesis, structures, characterization, and applications to field-effect transistors (FETs) of naphtho[1,2-b:5,6-b′]dithiophene (NDT) and -diselenophene (NDS) derivatives. Treatment of 1,5-dichloro-2,6-diethynylnaphthalenes, easily derived from commercially available 2,6-dihydroxynaphthalene, with sodium chalcogenide afforded a straightforward access toNDTsand NDSsincluding the parent and dioctyl and diphenyl derivatives. Physicochemical evaluations ofNDT and NDS derivatives showed that these heteroarenes have a similar electronic structure with isomeric benzothieno[2,3-b]benzothiophene (BTBT) and  benzoselenopheneno[2,3-b]benzoselenophene (BSBS) derivatives, respectively. Although attempts to fabricate solution-processed field-effect transistors (FETs) with soluble dioctyl-NDT (C8-NDT) and -NDS (C8-NDS) failed, diphenyl derivatives (DPh-NDTand DPh-NDS) afforded vapor-processed FETs showing field-effect mobility as high as 0.7 cm2 V-1 s-1. These results indicated that NDT and NDS are new potential heteroarene core structures for organic semiconducting materials.