An aqueous base-soluble polyimide (BAPAF/6FDA) was obtained from the polycondensation of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BAPAF) and 4,4＇-(hexafluoroisopropylidene)-bis(phthalic anhydride (GFDA). It exhibits high thermal stability and high transparency at 365 nm. A novel positive photoresist was prepared by protecting BAPAF/GFDA with a trimethylsilyl group while using diazonaphthoquinone as the photosensitizer. In addition, the silylated polyimide was converted to aqueouse base-soluble polyimide in the presence of an acid and a slight amount of water. This photoresist yields a sensitivity of 110 mJ/cm(2) and a contrast of 3.24.