In this paper we consider the entrance pathway of a collision between an atom and a polar molecule oriented by a strong electric field. This orientation technique, developed by Loesch and co-workers, can be applied to a large manifold of molecules to study the stereodynamics of their reactive collisions. As the atom is approaching the oriented molecule, a competition between the molecule-external field and atom-molecule interactions takes place and a reorientation of the molecule may occur. The intense external field may also change the dynamics of the collision process. These two questions are discussed on a general basis, and this discussion is illustrated in the case of the K + IC1 reactive collision.