A series of phenylene-fluorene derivatives see tigure) are synthesized and evaluated for use in organic field-effect transistors. Average field-effect mobilities as high as 0.32 cm(2) V-1 s(-1) are achieved by vacuum deposition at low substrate temperatures. The high ionization potentials in the derivatives lead to improved chemical and photostability. Transistor devices show no loss in performance when tested over a period of three months.