An analytical and experimental investigation of the radiation properties of wide-flare corrugated E-plane sectoral horns (10° < α0 < 70°, where ao is the half-flare angle) excited in the HE11 mode [1] with improved E-plane radiation patterns and suppressed side-lobe levels over a broad bandwidth is described in this paper. Given the flare length and half-flare angle of the horn, the far-field radiation pattern is determined by two methods, one of which involves aperture-field integration, based on vector diffraction formula over a constant phase surface at the mouth of the horn and the other of which employs an expansion of the aperture field in terms of free-space cylindrical TE and TM wave functions. Good agreement is obtained between the two methods with measured radiation patterns for several values of α0. Given the flare length, variation of the on-axis gain with α0of the horn is analytically investigated, and the design procedure for determining optimum α0, in order to obtain maximum on-axis gain, is also indicated. Further-more, design and experimental studies on wide-flare horns under consideration are also summarized. Copyright © 1974 by The Institute of Electrical and Electronics Engineers, Inc.