The invention relates to the use of oxime sulfonates of formula 1 ##STR1## wherein R is naphthyl, ##STR2## Ar is an unsubstituted aryl group or an aryl group which carries one or more than one substituent selected from the group consisting of nitro, chloro, bromo, hydroxyl, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 perfluoroalkyl, C.sub.1 -C.sub.4 alkoxy and acid degradable substituents;R.sub.0 is either a R.sub.1 --X group or R.sub.2 ;X is an oxygen or a sulfur atom;R.sub.1 is hydrogen, C.sub.1 -C.sub.4 alkyl or unsubstituted phenyl or phenyl which is substituted by a member selected from the group consisting of chloro, bromo, C.sub.1 -C.sub.4 alkyl and C.sub.1 -C.sub.4 alkoxy, andR.sub.2 is hydrogen, C.sub.1 -C.sub.4 alkyl or an acid-degradable substituent, as radiation-sensitive photoacid generator in a chemically amplified photoresist which is developable in alkaline medium and is sensitive to radiation of a wavelength in the range from 340-390 nm, and to corresponding positive-working and negative-working photoresists for the cited wavelength range.