Ab initio SCF calculations have been carried out on the fluoride exchange reaction F-+CH3F→FCH3+F-. An external uniform electric field along the FCF axis has been incorporated by proper changes in the one-electron part of the Fock matrix. The reaction profile has been found to be dramatically modified with increase in strength of the applied field. The electric field is found to be essential to describe the potential energy hypersurface so that it intervenes in the reaction coordinate. It is concluded that strong electric fields open a new way to catalyze reactions. © 1988.