Bis(octylthio) derivative of alpha-dithienotetrathiafulvalene (alpha-DT-TTF) was synthesized, characterized, and examined as a semiconductor for organic field-effect transistors (OFETs). In contrast to no field-effect responses of devices based on evaporated thin-film of the parent alpha-DT-TTF, the octylthio derivative afforded solution-processed OFETs showing apparent normally-on behaviors with field-effect mobility of up to 0.6 cm(2)V(-1)s(-1). Characterization of the thin-film revealed that the octylthio groups had significant impact on self-assembly, affording high quality thin films with well-oriented molecular array.