We have prepared and characterized thin film field effect transistors (FETs) of bis-(1, 2, 5-thiadiazolo)-p-quinobis(1, 3-dithiole) (BTQBT) and its derivatives. Preparation and characterization of the films were carried out under ultrahigh vacuum condition. Most materials examined showed p-type semiconducting behaviors. Among p-type molecules, BTQBT films deposited at room temperature showed the highest mobility and on/off ratio of 0.2 cm2/Vs and 108, respectively, at optimal film growth conditions. These performances are almost comparable to those of pentacene and polythiophene thin films, indicating that BTQBT molecule is a prominent semiconducting material for high-speed organic transistors. It was also found that a tetracyanoquinodimethane (TCNQ) derivative showed an n-type semiconducting behavior with an electron mobility of 8.9 x 10-4 cm2/Vs.