The term askarel generally describes a widely used broad class of nonflammable synthetic halogenated hydrocarbon insulating liquids. In this guide, it applies solely to askarel in transformers, reactors, and accessory equipment operated at power frequencies. Transformer askarels contain PCB's (polychlorinated biphenyls), which have been used in the United States and elsewhere over the past 40 years for many industrial and consumer applications. Recently, evidence has accumulated to indicate that PCB's are widely dispersed throughout the environment and that they can have adverse ecological and toxicological effects. The Federal Interdepartmental Task Force report COM-72-10419, 'Poly chlorinated Biphenyls and the Environment/* dated May 1972, has recommended restricting PCB's to use in transformers and capacitors. Methods for handling and disposal of askarels and askarel-impregnated materials are given in Draft American National Standard, Guidelines for Handling and Disposal of Capacitor and Transformer-Grade Askarels Containing Polychlorinated Biphenyls, C107.1 This guide assists the power equipment operator in evaluating askarel as received in transformers, reactors, and accessory equipment operated at power frequencies and in his efforts to maintain askarel in serviceable condition. It recommends standardized tests and evaluation procedures. Methods are outlined for reconditioning and reclaiming askarel whenever necessary.