The electropolishing of tantalum in sulfuric acid-methanol electrolytes is studied by steady state measurements and ac impedance spectroscopy using a rotating disk electrode. The effects of electrolyte composition, applied potential, electrode rotation rate and temperature on the response of the system are investigated. Steady state measurements performed at different temperatures show that at the limiting current plateau the rate of dissolution is controlled by mass transport of Ta5+ species from the anode to the bulk electrolyte. The impedance data obtained under limiting current conditions suggest the presence of a compact film through which tantalum ions migrate by high-field conduction.