We present a theoretical study of controlling molecular chirality in chemical reactions by circularly polarized fields. A theory of absolute asymmetric synthesis is formulated by standard perturbation theory. An estimation of the chiral polarization of the product is provided. We show that an unstable chiral configuration can be described as a spin one-half particle. The circularly polarized field with well adjusted parameters is applied to stabilize chiral molecules (destruction of quantum coherence in the two-level system). (C) 1997 American Institute of Physics. [S0021-9606(97)01846-1].