If we desire to gage the difficulties encountered in judging and testing polymeric insulation, we should remember that, generally speaking, the poorer the electric characteristics of these materials, the better will be their mechanical and thermal qualities. Perhaps this has not been so noticeable in the case of the classic insulating materials, such as rubber and fibers. However, reduction in insulating resistance is the deciding factor with soft PVC where, as is well known, addition of softener will bring about a corresponding ability to withstand cold and bending. It is therefore necessary in this case to select the type and content of softener so that adequate thermal and mechanical characteristics are attained without loss of electric dependability. Also with other polymers, the additives used to improve mechanical and thermal qualities are unfavorable electrically. The test methods used in evaluating cable insulations must make possible the stipulation of optimum compounds. Therefore numerous individual tests must be made, so as to arrive at reliable conclusions in every respect. Table I gives a tabulation of the tests prescribed in Germany for cables with plastic insulation and cover. If special requirements must be met such as, for instance, resistance to chemicals or to ozone, additional tests may be prescribed. Test requirements in other countries are even more comprehensive than in Germany. Such extensive tests render more difficult any evaluation of polymeric cable insulations. They require much time and effort, especially when series of tests are involved in the case of newly developed materials. Inasmuch as each test brings out only a small part of the pertinent characteristics of the material and none can be ignored, it follows that the overall evaluation becomes difficult. It should be in order, therefore, to ask whether it is possible, by means of one single measuring method, to obtain at least a comparative survey of all determining characteristics of such high polymer insulating materials. Potthoff has mentioned, among other things, that too little use is made of the fact that carrying out simple and nondestructive measurements of the frequency and temperature dependent dielectric loss factor permits a deep insight into the characteristics of insulating materials. Actually, this measurement affords the means of grasping the most interesting influences involved with the least effort.