Perfluorinated hydrocarbons, because of their chemical inertness and thermal stability, have been used for a number of years in a limited number of applications in the electrical and electronic industries. Recently, a new family of perfluorinated ethers has become commercially available. Physical properties of this new family of insulating fluids include non‐flammability, high density and a wide range of viscosities. The physical and electrical properties of two representative samples of this family have been studied in detail and compared with those of other insulating oils. The results of this study suggest that these fluids should be of considerable interest to the electrical industry, particularly in applications requiring a high degree of fire protection combined with environmental compatibility.