The problem of the propagation of electromagnetic waves along a dielectric cylinder of elliptical cross section is considered. There exist two dominant waves which possess zero cutoff frequencies. The attenuation characteristics of these dominant waves are analyzed theoretically and experimentally. Good agreements are obtained. It is shown that one of the dominant waves, with its electric fields parallel at the center of the cylinder to the minor axis of the elliptical cylinder, can propagate along a flat dielectric strip with much lower loss than can the

wave along a circular cylinder having the identical cross-sectional area.