The radiation and scattering characteristics of a parallel-plate waveguide backed slot in a ground plane, coupled to a chiral cylinder, are investigated. The excitation is either a transverse electromagnetic (TEM) mode wave within the guide or a uniform, E- and H-polarized, plane wave incident in the exterior region. Coupled integral equations are developed to determine the cross-polar effect due to the chirality of the load. Numerical data are presented for the aperture electric field, radiation efficiency, far-fields, and the received power for the guide, which support only TEM mode.