[en] A general theory for coupling between MHD waves obliquely incident on a stratified medium is developed. Coupling between the Alfven mode and the magnetoacoustic mode (the fast mode for upsilonsub(A) > csub(s) and the slow mode for upsilonsub(A) < csub(s) is affected little by the finiteness of csub(s)/upsilonsub(A) for upsilonsub(A) >> csub(s), and the coupling becomes weakers as csub(s)/ upsilonsub(A) is increased towards unity. Coupling between the fast and slow modes for upsilonsub(A) approximately equal to csub(s) is discussed qualitatively using solutions of the MHD counterpart of the Booker quartic equation. (Author)