Five new phenoxazine-based conjugated polymers, including poly(10-hexylphenoxazine-3,7-diyl), poly(10-hexylphenoxazine-3,7-diyl-alt-9,9-dihexyl-2,7-fluorene), and poly(10-hexylphenoxazine-3,7-diyl-alt-3-hexyl-2,5-thiophene), were synthesized, characterized, and successfully used as p-channel semiconductors in organic field-effect transistors. The polymers have high glass transition temperatures in the 112-230 degrees C range. The phenoxazine-based polymers have low ionization potentials or high-lying HOMO levels (4.8-4.9 eV), which were estimated from cyclic voltammetry. Organic field-effect transistors based on the phenoxazine polymer semiconductors have a field effect hole mobility of up to 6 x 10(-4) cm(2)/(V s) and an on/off ratio of up to 10(4). These results demonstrate that phenoxazine-based conjugated polymers are promising p-type semiconductors for solution processable thin film transistors.