The synthesis. thin-film morphology, and hole mobility in thin-film transistors (TFTs) of compounds based on the novel anthradithiophene (ADT) ring system are reported. The parent compound and its 2,8-dihexyl, didodecyl, and dioctadecyl derivatives (DHADT, DDADT, and DOADT, respectively), synthesized via alkylated thiophene dicarboxaldehyde acetals, were investigated. They all form highly ordered polycrystalline vacuum-evaporated films with mobilities as high as 0.15 cm(2)/(V s), as high as has ever been observed for a polycrystalline organic material. DOADT has a mobility of 0.06 cm(2)/(V s) even though 70% of its molecular volume is occupied by hydrocarbon chains. DHADT was cast from solution under atmospheric conditions onto a TFT giving a mobility of 0.01-0.02 cm(2)/(V s), Thus, the alkylated ADTs combine a pentacene-like intrinsic mobility with greater solubility and oxidative stability.