In order to obtain filters capable of handling very high power, the use of radial lines and uniform line discontinuities was investigated as the most promising approach. In this connection, it was necessary to consider equivalent circuit and interaction effects for H-mode radial line mated at each end to uniform TE 10 waveguide for taper angles of 45 degrees. It was found that the equivalent circuit was valid for taper angles of 45 degrees, and that for engineering design purposes the interaction could be neglected. The author utilized the 45° tapers and the uniform lines to design a high power microwave filter capable of handling 700 kilowatts at 10 pounds pressure in 0.900 by 0.400 I.D. waveguide. The design procedure for a multi-element filter is described utilizing a partly graphical approach.