An all-polymer field-effect transistor (FET) fabricated using air inkjet printing technique is presented in this paper. Poly(3,4-ethylenedioxythiophene) works as the source/drain/gate electrode material because of its good conductivity. Polypyrrole acts as the semiconducting layer. Poly(vinyl pyrrolidone) K60, an insulating polymer with a dielectric constant of 60, operates as the dielectric layer. All the polymers are diluted with deionized water, and can be printed with a piezoelectric inkjet printing system. The device functions at a depletion mode with 2 low operation voltage. It has a field-effect mobility of 0.1 cm(2) center dot V-1 center dot s(-1), an on/off ratio of 2.9 x 10(3), and a subthreshold slope of 2.81 V center dot decade(-1).