The demand for high quality, stereo telephony conferencing systems has led to increased research activities in the field of stereo echo cancellation. The fundamental problem is caused by two highly correlated source signals, which makes it almost impossible to uniquely identify two loadspeaker-room-microphone (LRM) systems. Most previous solutions try to solve this problem by a modification of the source signals. In this paper we propose a postfilter, which has already successfully been used for mono acoustic echo cancellation. The postfilter is placed in the sending path of the system to attenuate the residual echoes remaining after a non-perfect echo cancellation and thus achieve a stronger total echo attenuation.