With the increasing interest and concern regarding the vibration of overhead conductors, and the emphasis on the improvement of existing methods and the development of new techniques for controlling the problem, there is a growing requirement for reliable information on the self-damping characteristics of conductors. This parameter is a principal factor in determining the response of conductors to alternating forces, such as arise from wind flow over conductors. This guideline has been prepared for the purpose of encouraging investigators contemplating making measurements of the inherent damping characteristics of conductors, to adopt the methods outlined herein. It is anticipated that the resulting information, being in a compatible and consistent form, will provide a reliable basis for studying the vibration and damping of conductors in the future and for the comparison of data of various investigators. The methods and procedures recommended are not intended for quality control test purposes. SI units are used throughout this document with the commonly employed English units shown in parentheses. There are several methods available for measuring the energy dissipated by a cable vibrating in a principal mode. These can be divided into two main groups which are usually referred to as the "free vibration" and "forced vibration" methods. The vibration of a cable in a principal mode can be observed only in the absence of any exciting force, that is, after the force has been disconnected and the other modes have decayed to insignificant values. The energy dissipated can then be derived from the rate of decay of the vibration. This method can be greatly affected by the method used to disconnect the driving force as the slightest additional disturbance of the conductor causes other vibration modes to be generated and this must be avoided. With the relatively low rates of decay which are usually associated with stranded conductors, the Forced vibration method is satisfactory as the contribution of the modes, other than the one which is being excited, is not significant if the frequency of the exciting forces corresponds closely to the resonant frequency of the mode under test and if the exciting force is substantially sinusoidal and of sufficiently low magnitude. Two forced vibration methods are therefore suggested