We deal with the scattering phenomenon from an abruptly terminated asymmetrical slab waveguide for the case of transverse magnetic (TM) modes. The analysis uses both the integral equation method and the variational technique. The reflection coefficient of the dominant TM guided mode and the far-field radiation pattern are computed, and the discontinuity of the electric field distribution on the core-clad interface is exhibited. Numerical results are presented for several cases of abruptly ended waveguides, including the three-layer slab guide and the structure with variable profile of the refractive index.