The zeta potential of bubbles generated by ultrasonication was determined for a range of frother types. At concentrations close to flotation practice (<20 ppm) the effect of frother was negligible. With increasing concentration (up to 100 ppm) F150 and pentanol decreased charge and MIBC and heptanol increased negative charge but the change remained small. An effect on bubble charge does not appear to contribute to the action of frothers, in particular the reduction in bubble size. The data are briefly discussed in light of models of bubble charging in water and in presence of non-ionic surfactants. (C) 2008 Elsevier B.V. All rights reserved.