The resolution of chiral compounds into enantiomers by irradiation with circularly polarized light is a clearly understood phenomenon. 1 If the two enantiomers of a compound are stable in the ground state but are interconverted in an electronically excited state, then irradiation of the racemic mixture with circularly polarized light can lead to the enrichment of one enantiomer. The degree of enrichment (enantiomeric excess, ee) and the rate atwhich the photostationary state is established depend on the Kuhn anisotropy factor (gx=

/ex). We have been searching for photoresolvable compounds with large values of gx so that their irradiation with circularly polarized light in liquid crystalline media will generate an ee sufficiently large to convert a nematic to a cholesteric phase. 2 Irradiation of such a cholesteric liquid crystal with unpolarized light will racemize the chiral compoundand regenerate the nematic phase. Thus, this liquid crystalline material may be switched between cholesteric and nematic phases by alternate irradiation with circularly polarized and unpolarized light. 3 If compounds suitable for this function are discovered, they may form a basis for development of an optical switch.