Loss measurements were made on ten dielectric coated wires used as surface wave transmission lines at a frequency of 9365 mc/sec. The purpose of these measurements was (1) to develop a satisfactory method for making the loss measurements, and (2) to compare the measured loss with the calculated or predicted value obtained from theoretical analysis made by Goubau. A resonance method, in which theQof a resonator formed by short circuiting both ends of a length of line is determined, was found to be most desirable. The loss in the resonator end plates was taken into account in determining the wire loss.A description of the apparatus required and the experimental procedures used is given. A brief discussion of alternative methods for making the loss measurements, some of which have been tried, is also given.The losses of the wires measured ranged from about 3.0 db/100 feet for thin dielectric coatings to about 11.5 db/100 feet for thick dielectric coatings. The agreement between measured and calculated losses of wires for which the constants of the dielectric coating are known is considered good.