During the d.c. electrolysis of KF-nHF melts, a passivating film of graphite fluoride (CFx) is formed on the carbon electrodes, leading to high anodic overvoltage. Pulsed electrolysis enables fluorine production with significant improvements if, during the lowest potential of the pulse, a small reduction current is applied to the carbon electrode, leading to the partial reduction of CFx. Rectangular or sinusoidal waves have been studied. Very high peak values of the current density (150 A dm−2,i.e. 10 times more than the values usually reached with d.c) were obtained in some particular cases.