Polyampholyte latexes that contain 29/18 and 25/23 mol % of (styrylmethyl)trimethylammonium/methacrylate units and styrene cross-linked with divinylbenzene are colloidally stable in 4 M NaCl solution. As catalytic media in basic solutions 0.5 mg mL(-1) of the polyampholyte latexes increase the rate of decarboxylation of 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) 60-115 times, while the precursor polycation latexes increase the rate 540-670 times the rate in water alone. The latexes are active catalysts in 0.67 M NaCl solution, but activity decreases as the concentration of added NaCl increases. Analysis of rate constants at varied particle concentrations indicates that the fractions of the 6-NBIC anions bound to particles are similar in the two types of latexes and that the differences in activity are due primarily to larger intraparticle rate constants in the polycation latexes than in the polyampholytes.