We analyze the coupled-mode propagation in planar gyrotropic chirowaveguides. At first, the transverse components of electric and magneticfields in such waveguides are expressed in terms of the longitudinal components of EBAR and HBAR. Dispersion diagrams for the parallel metallic-plate gyrotropic chirowaveguides are shown, and their novel features are pointed out. The effects of chirality admittances on the cutoff wavelengths of propagating modes in the grounded planar and parallel metallic-plate gyrotropic chirowaveguides are taken into consideration. (C) 1993 John Wiley & Sons, Inc.