Although the title of the paper refers only to copper conductors, copper-alloy and steel-reinforced copper conductors for use on overhead lines are included. The creep of conductors and their initial non-elastic extension are considered in relation to their effect on sags and their compensation by an increase in erection tension as analternative to pre-stressing. A typical stress/strain curve for copper conductors is given.Information on the annealing characteristics of hard-drawn copper and copper-alloy conductors is included, with special reference to the effect of impurities in the metal. Maximum safe operating temperatures for such conductors are discussed, together with maximum permissible current loadings.Hollow copper conductors of various types for voltages up to 200–300 kV are described and some of their characteristics enumerated. The features of cadmium-copper conductors are dealt with in comparison with other types of high-tensile overhead conductor.Steel-reinforced copper conductors receive special attention, particularly in regard to the protection from corrosion of the steel wires. Results of a long-time investigation are given in full, with conclusions and recommendations. Copper-clad steel wires, their characteristics and use as reinforcement in copper conductors, are discussed.Details are given of developments in the application of compressed sleeve joints to copper and copper-alloy conductors. Suitable joints for cadmium-copper and steel-cored copper conductors are described and test results given.