High mobility ambipolor polymer field-effect transistors based on a series of regioregular polyselenophenes are presented together with their morphological and optical properties. Balanced electron and hole mobilities on the order of 0.03 cm(2)V(-1)s(-1) are observed by employing a simple top-gate/bottom-contact configuration with photolithographically defined gold source/drain contacts. High gain complementary-like voltage inverters are demonstrated based on two identical ambipolar transistors.