Abstract: An alkaline aqueous developing solution for developing photoresists or the like contains, as an anti-scum agent: A) between about 0.05 and about 1.0 wt % of a first surfactant or surfactant mixture, the first surfactant(s) having the general formula: R—O—(AO)n—H where AO are alkylene oxide units selected from ethylene oxide units (CH2—CH2—O) and propylene oxide units (CH(CH3)—CH2—O) or (CH2—CH(CH3)—O) and mixtures of ethylene and propylene oxide units, either in the mixture of molecules, where R is a hydrophobic group, n is between about 8 and about 200, and B) as a second surfactant, between about 0.05 and 1.0 wt % of an organic salt having the formula: where R is an alkyl or aryl group, preferably phenyl, A is selected from carboxyl, sulfonyl, phosphonyl and mixtures thereof, preferably sulfonyl. M is a charge-balancing cation, and n is between 1 and about 200, preferably between 2 and about 100.