Abstract: The properties of an inclined slot, rediating in free space, on the center line of the broad face of a waveguide are discussed. The integral equations are dirived from continuity conditions of the tangetial fields, taking into account the waveguide wall thickness. A moment method is used to slove these equations numerically by means of a computer, thereby obtaining fields at the slot surfaces, the scattering fields and the general formulas of the scattering parameters as well as the equivalent impedances. The parameters of scattering and equivalent impedances at different frequencies are calculated in the X-band, the resonant resistances and the resonant lengths as a function of the inclination angle, the well thickness and the frequency are given also. The calculated results are in good agreement with those obtained experimentally.