The paper consists of two parts. The first is devoted to a comprehensive review of overhead-conductor sags and tensions and their calculation on single spans and on complete lines, using parabolic formulae throughout. A standard procedure and standard methods of calculation are recommended.The second part of the paper deals with the determination, from the point of view of the conditions prevailing in Great Britain, of wind and ice loads to be applied to conductors for design purposes and the stresses so produced in the conductors. The use of the term “factor of safety” when applied to overhead conductors is criticized, and suggestions are offered for revisions to the Overhead Line Regulations of the Electricity Commissioners. The loads transmitted to the supports are also considered. Erection sags for low-voltage distribution lines are recommended for general adoption.