The bare concentric neutral wires of underground electric distribution cables corroded in soils not regarded as corrosive. The tinned copper wires are important for safety and electrical integrity of the 7. 2 kV cables. Test data from four electric systems in America show consistent relationships betwen corrosion and measured d. c. potentials; copper is likely to be corroding where potentials to earth are zero or positive with reference to a copper-copper-sulfate half-cell, and is in danger of corrosion at potentials less negative than -- 0. 1 volt. Copper corrosion in soil, once it has started, is likely to be relatively rapid, but cathodic protection by sacrifical anodes or by the use of steel ground rods is considered a feasible and economical means of prevention. However, additional experience is needed to define the current requirements and give better criteria for cathodic protection. -- AATA