A cyclic triphenylamine dimer with highcrystallinity is demonstrated. Micrometer-and nanometer-sized single-crystalline ribbons are easily produced by a physical vapor transport technique. Field-effect transistors of the ribbons exhibit mobilities up to 0.05 cm(2) V-1 s(-1). The mobility of the devices depends greatly on the size of the ribbons: the smaller the ribbons, the higher the mobility.