A new photoacid generator having the formula ##STR1## wherein R=hydrogen, hydroxyl, or the --O--S(.dbd.O).sub.2 --Q moiety;R.sup.1 =CH.sub.2 OS(.dbd.O).sub.2 --Q, or --NO.sub.2 ;R.sup.2 =CH.sub.2 OS(.dbd.O).sub.2 --Q, or --NO.sub.2 ;R.sup.3 =lower alkyl or hydrogen;R.sup.4 =hydrogen, --CH.sub.2 OS(.dbd.O).sub.2 --Q, or --NO.sub.2 ;R.sup.5 =hydrogen, --CH.sub.2 OS(.dbd.O).sub.2 --Q, or --NO.sub.2 ; andQ is a diazonaphthoquinone moiety; with the proviso that R.sup.3 is lower alkyl when R.sup.2 and R.sup.4 are NO.sub.2, and with the proviso that R.sup.1 .noteq.R.sup.2 and R.sup.4 .noteq.R.sup.5.exhibits unprecedented sensitivity to actinic radiation. This compound is photochemically transformed from a non-acidic entity to photoproducts which contain both sulfonic and carboxylic acid functuional groups. The acid generator is effective with polymers having acid labile groups, converting them into alkaline-soluble polymers, and with polymers which do not have such acid labile groups. Positive or negative working photoresist compositions containing the new photoacid generator have unparalleled performance characteristics because of the increased acidity generated per quantum of light.A preferred photoacid generator is made by reacting 2,6-dimethylol-3,5-dinitro-p-alkyl phenol with a diazonaphthoquinone sulfonyl chloride.