In recent years most of the emphasis in plume modeling has been directed at improving the entrainment equations while the non-entrainment equations (momentum, energy, state, etc.) have been thought to be firmly established. In the report, it is shown that serious deficiencies remain in the non-entrainment equations. Inclusion of center-of-mass concepts, element overlap, and asymmetric entrainment shows that substantial changes in dilution predictions are effected by these corrections. Consequently, it is inappropriate to develop elaborate entrainment functions until these deficiencies are corrected.