The effect of an applied electric field on the mobilities of carboxyl-terminated dendrimers has been measured by capillary electrophoresis at applied voltages V ranging from 5 to 30 kV. The mobility increased with the field strength at moderate ionic strength, but varied inversely with V at low ionic strength. These results did not arise from Joule heating or from electroosmotic flow effects. It is suggested that the remarkably high velocities of these dendrimers enables them to outstrip their ion atmospheres at high V, in a manner related to the increase in conductance at high field strength first described by Wien in 1927. At low ionic strength, the increase in the size of the ion atmosphere leads to increased frictional drag with increasing field strength.