The current distribution at the electrodes in an industrial aluminium cell with prebaked anodes was calculated. The difference between the primary and secondary current distribution was determined for three different gaps between anodes or between anode and sidewall (2.5, 10 and 30 cm). The calculated current densities at the vertical sides of the anode were higher for the secondary current distribution than for the primary (almost double at the uppermost part of the anode), while the differences were much smaller at the cathode (6–20%). If the conducting carbon sidelining is exposed to the electrolyte it will draw an average current density of 0.045 A cm−2 for a 30 cm distance to the cathode. If all this current leads to the formation of aluminium carbide with subsequent dissolution into the electrolyte, the sidelining will corrode at a rate of 0.08 cm d−1 of exposure. The influence of the shape and position of the ledge on the anode current distribution was studied. When the distance between the ledge and anode was greater than 15 cm the shape of the sideledge does not affect the anode current densities significantly, while the current density at the upper part of the anode increases with increasing distance.