Poly(vinylidene fluoride) (PVDF) films were irradiated with 450 MeV 129 Xe and 2.2 GeV 197 Au ion beams, and then the resulting latent tracks were etched in a 9 mol dm -3 aqueous KOH solution at 80ºC that had been poured into a conductometric cell. At the same time, the evolution of cylindrical nanopores was monitored by measuring the conductance through the membrane. This in-situ measurement enabled us to examine how the etching kinetics were affected by the various experimental conditions including the parameters (mass and velocity) of the bombarded ions and cell voltages applied between the electrodes. The track etch rate, V T , radial etch rate, V R , and pore radius reaching the final plateau significantly depended on the deposited energy within each track, which is represented by the linear energy transfer (LET). Interestingly, applying a higher voltage to the cell promoted track etching up to the breakthrough probably because the electrophoretic migration of dissolved products occurred out of each pore.