National Implementation Plan for reduction and elimination of persistent organic contaminators in our country, prepared in accordance to the Stockholm Convention, requires identification, detail mapping and quality analysis of transformer oils and liquid dielectrics. Until now, the National Plan gets into consideration as potential contaminants only insulating oils for power transformers in industrial and power systems. Therefore, the need for establishing the mechanisms for quality control and environmental impact of high-voltage insulating oils used in X-ray generators appears. These mechanisms are developed in the Protocol, presented in the paper, as a physical and chemical analysis of new and used oils in X-ray generators. The results from the analysis of several samples of used and new insulating oils show that their quality is correlated with the time of exploitation and working conditions. The analysis of investigated samples clearly show that the presence of polychlorinated biphenyls in used oils could be a signal for introducing a special measures and treatment during the services and maintenance of X-ray generators. The aim of the Protocol is to determine the equipment which could be potential contaminator of environment, to establish regulative for continuous quality control and to introduce environmental, healthy and safe measures for high-voltage insulating oils, used in X-ray generators.