The anodic oxidation of potassium bromide to potassium bromate is performed in an undivided cell with hydrogen evolution the major reaction at the counter electrode. The cell used is a dished electrode membrane (DEM) cell. Current density distribution, measured using a segmented electrode, shows a variation in the two principle dimensions; along the length of the electrode and over the width of the electrode. Current densities are highest at the electrolyte flow inlet and also exhibit a localized maximum along the electrode length. The variation in current density is due to the influence of electrolytic gas evolution on the effective electrolyte conductivity and mass transport and also due to the change in shape of the dished electrode, which influences mass transport, electrical potential field and flow at the cell inlet and exit.