Organic thin-film transistors were fabricated by direct patterning of solution-processable semiconductors consisting of either poly(9,9(')-dioctyl-fluorene-co-bithiophene) or a regioregular poly(thiophene). Acoustic ink-jet printing was used to deposit the polymeric semiconductor onto patterned metal source-drain contacts. Printed and spin coated transistors performed identically. The regioregular poly(thiophene) exhibited a mobility of 0.1 cm(2) V-1 s(-1), on-off current ratios of similar to10(6) and low threshold voltage. (C) 2003 American Institute of Physics.