The establishment of suitable criteria for the evaluation of the radiation resistance of insulating materials is very complex, since such criteria depend upon the conditions under which the materials are used. For instance, if an insulated cable is flexed during a refuelling operation in a reactor, the service life will be that time during which the cable receives a radiation dose sufficient to reduce to a specified value one or more of the relevant mechanical properties. Temperature of operation, composition of the surrounding atmosphere and the time interval during which the total dose is received (dose rate or flux) are important factors which also determine the rate and mechanisms of radiation-induced chemical changes. In some applications, temporary changes are the limiting factor. Given this, it becomes necessary to define the radiation fields in which materials are exposed and the radiation dose subsequently absorbed by the material. It is also necessary to establish procedures for testing the mechanical and electrical properties of materials which will define the radiation degradation and link those properties with application requirements in order to provide an appropriate classification system. The present part of the IEC 60544 series is the introductory part to a series dealing with the effects of ionizing radiation on insulating materials. IEC 60544-2 describes procedures for maintaining different environmental conditions during radiation. Moreover, the controls to be maintained over these conditions in order to obtain the desired stress are specified. Furthermore, a number of potentially significant irradiation conditions as well as various parameters which can influence the radiation-induced reactions under these conditions are specified. IEC 60544-4 defines a classification system to categorize the radiation endurance of insulating materials. It provides a set of parameters characterizing the suitability for radiation service, and it is a guide for the selection, indexing and specification of insulating materials. Finally, IEC 60544-5 gives guidance for the assessment of ageing in service and examples and restrictions for the different procedures of condition monitoring. The standard IEC 60544-1 deals with dosimetry and examinations carried out in irradiation facilities for evaluation and testing of material characteristics and properties. Dosimetry that might be carried out at locations of use of the material is not described in this standard. Furthermore, the standard deals broadly with the aspects to be considered in evaluating the effects of ionizing radiation on all types of organic insulating materials. It also provides, for Xrays, γ-rays, and electrons, a guide to dosimetry terminology, methods for dose measurements, and for documenting the irradiation process. The responsible committee is DKE/K 183 "Bewertung und Qualifizierung von elektrischen Isolierstoffen und Isoliersystemen" ("Evaluation and qualification of electrical insulating materials and systems") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.